Light-emitting device, method of manufacturing a light-emitting device, and electronic equipment

ABSTRACT

The present invention uses plastic film in vacuum sealing an OLED. Inorganic insulating films which can prevent oxygen or water from being penetrated therein and an organic insulating film which has a smaller internal stress than that of the inorganic insulating films are laminated on an inside of the plastic film. By sandwiching the organic insulating film between the inorganic insulating films, a stress can be relaxed. Further, by laminating a plurality of inorganic insulating films, even if one of the inorganic insulating films has a crack, the other inorganic insulating films can effectively prevent oxygen or water from being penetrated into an organic light emitting layer. Further, the stress of the entire sealing film can be relaxed and cracking due to the stress takes place less often.

This application is a continuation of U.S. application Ser. No.10/976,988 filed on Oct. 29, 2004 now U.S. Pat. No. 7,067,976 which is adivisional of U.S. application Ser. No. 10/183,282, filed on Jun. 27,2002 now U.S. Pat. No. 7,129,102.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the fabrication method of Semiconductordevice and specially relates to a light-emitting device which includesan OLED (organic light-emitting device) panel which is formed on aplastic substrate. The invention also relates to an OLED module obtainedby mounting an IC that includes a controller to the OLED panel. In thisspecification, a light-emitting device is used as the generic term forthe OLED panel and the OLED module. Also included in the presentinvention is electronic equipment using the light-emitting device.

2. Description of the Related Art

In recent years, a technique of forming a TFT (Thin film transistor) ona substrate has made great advancement to promote application of TFTs toactive matrix display devices. In particular, TFTs using polysiliconhave higher field effect mobility (also called mobility) thanconventional TFTs that use amorphous silicon and therefore can operateat high speed. This makes it possible to control pixels, which hasconventionally been controlled by a driving circuit external to thesubstrate, by a driving circuit formed on the same substrate on whichthe pixels are formed.

With various circuits and elements formed on the same substrate, activematrix display devices can have many advantages including lowering ofmanufacture cost, reduction in display device size, an increase inyield, and improvement in throughput.

An active matrix light-emitting device having an OLED as a self-luminouselement (hereinafter simply referred to as light emitting device) isbeing researched actively. A light-emitting device is also called as anorganic EL display (OELD) or an organic light emitting diode (OLED).

Being self-luminous, an OLED does not need back light which is necessaryin liquid crystal display devices (LCDs) and is therefore easy to make athinner device. In addition, a self-luminous OLED has high visibilityand no limitation in terms of viewing angle. These are the reasons whylight emitting devices using OLEDs are attracting attention as displaydevices to replace CRTs and LCDs.

An OLED has a layer containing an organic compound (organic lightemitting material) that provides luminescence (electroluminescence) whenan electric field is applied (the layer is hereinafter referred to asorganic light emitting layer), in addition to an anode layer and acathode layer. Luminescence obtained from organic compounds isclassified into light emission upon return to the base state fromsinglet excitation (fluorescence) and light emission upon return to thebase state from triplet excitation (phosphorescence). A light-emittingdevice according to the present invention can use one or both types oflight emission.

In this specification, all the layers that are provided between an anodeand a cathode of an OLED together make an organic light-emitting layer.Specifically, an organic light-emitting layer includes a light-emittinglayer, a hole injection layer, an electron injection layer, a holetransporting layer, an electron transporting layer, etc. A basicstructure of an OLED is a laminate of an anode, a light-emitting layer,and a cathode layered in this order. The basic structure can be modifiedinto a laminate of an anode, a hole injection layer, a light-emittinglayer, and a cathode layered in this order, a laminate of an anode, ahole injection layer, a light emitting layer, an electron transportinglayer, and a cathode layered in this order, or the like.

Various applications of such light-emitting device are expected. Inparticular, applications to portable equipment are attracting attentionbecause the light-emitting device is thin and accordingly is useful inreducing the weight. This has prompted attempts to form an OLED on aflexible plastic film.

A light-emitting device in which an OLED is formed on a flexiblesubstrate such as a plastic film is thin and light-weight and moreover,applicable to a curved display or show window, etc. Therefore, the usethereof is not limited to portable equipment and its application rangeis very wide.

However, plastic substrates in general are well transmissive of moistureand oxygen, which accelerate degradation of organic light emittinglayers. Therefore plastic substrates often shorten the lifetime oflight-emitting devices. This is solved in prior art by placing aninsulating film such as a silicon nitride film or a silicon oxynitridefilm between a plastic substrate and an OLED to prevent moisture andoxygen from entering an organic light emitting layer.

Plastic film substrates in general are also weak against heat and areeasily deformed if the insulating film such as a silicon nitride film ora silicon oxynitride film is formed at a temperature that is too high.On the other hand, if the temperature at which the insulating film isformed is too low, the quality of the film is reduced and the filmcannot prevent transmission of moisture and oxygen satisfactorily.

When the insulating film such as a silicon nitride film or a siliconoxynitride film is increased in thickness in order to preventtransmission of moisture and oxygen, the internal stress is increased tolikely cause a crack (fissure). The thick insulating film makes thesubstrate weak against cracking when the substrate is bent.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above, and an objectof the present invention is therefore to provide a light-emitting devicewith an OLED formed on a plastic substrate which is capable of avoidingdegradation due to transmission of moisture and oxygen.

The present invention relates to a technique of sealing an OLED formedon a substrate that has an insulating surface. According to the presentinvention, the OLED is sealed by vacuum sealing using a plastic filmthat is lined with layers of insulating films on the inside. The layersof insulating films include at least an insulating film which is made ofan inorganic material and which is capable of preventing transmission ofoxygen and moisture (hereinafter referred to as inorganic insulatingfilm), and an insulating film which is made of an organic material andwhich is smaller in internal stress than the inorganic insulating film.

Specifically, two or more layers of inorganic insulating films areformed and an organic insulating film containing a resin is placedbetween the inorganic insulating films. A bag-like plastic film linedwith the three or more layers of insulating films on the inside is usedto house a substrate on which an OLED is formed to seal the OLED andcomplete the light-emitting device.

In order to enhance the softness of the plastic film having theinorganic insulating films, the internal stress of the inorganicinsulating films may be relaxed by adding a noble gas element toreaction gas for forming the inorganic insulating films.

The present invention employs a plurality of layers of inorganicinsulating films. Therefore, if one inorganic insulating film iscracked, the other inorganic insulating films effectively preventmoisture and oxygen from entering an organic light-emitting layer. Withthe plurality of layers of inorganic insulating films, the presentinvention can effectively prevent moisture and oxygen from entering anorganic light-emitting layer even when the quality of the inorganicinsulating films is degraded by low temperature during formation of theinorganic insulating films.

The internal stress of the insulating films can be relaxed when anorganic insulating film that is smaller in internal stress than theinorganic insulating films is interposed between the inorganicinsulating films. Compared to a single layer of inorganic insulatingfilm having the same thickness as the total thickness of the inorganicinsulating films sandwiching the organic insulating film, cracking dueto the internal stress takes place less frequently in the inorganicinsulating films sandwiching the organic insulating film.

By layering the inorganic insulating films and the organic insulatingfilm, the flexibility is increased and cracking upon bending can beavoided.

The laminate of the inorganic insulating films and organic insulatingfilm (hereinafter referred to as sealing film) is formed by vacuumpress-fitting so that it is closely fit to the substrate on which theOLED is formed. Accordingly, the sealing film is a film having a certaindegree of softness and transparency or translucency to visible light.

In this specification, being transparent to visible light means having avisible light transmittance of 80 to 100%, and being translucent tovisible light means having a visible light transmittance of 50 to 80%.

In the above structure, it is preferable to place a drying agent betweenthe substrate on which the OLED is formed and the vacuum-sealed plasticfilm in order to prevent degradation of the OLED. A suitable dryingagent is barium oxide, silica gel, or the like. The drying agent can beput in a place before or after the flexible printed substrate is bonded.Alternatively, the drying agent may be placed in a flexible film of theflexible printed substrate before bonding the flexible printedsubstrate. The location of the drying agent is preferably the vicinityof the point of vacuum press-fitting of the plastic film.

In this specification, an OLED panel is not finished until its OLED issealed with a plastic film. However, the term OLED panel may refer toone before plastic film sealing.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings;

FIGS. 1A to 1C are diagrams of a light-emitting device of the presentinvention with FIGS. 1A and 1B showing sectional views thereof and FIG.1C showing a top view thereof;

FIG. 2 is a diagram showing apparatus for forming a sealing film;

FIGS. 3A to 3C are diagrams illustrating a method of sealing alight-emitting device of the present invention:

FIGS. 4A to 4C are diagrams showing a method of manufacturing alight-emitting device according to the present invention;

FIGS. 5A to 5C are diagrams showing a method of manufacturing alight-emitting device according to the present invention:

FIGS. 6A to 6D are diagrams showing a method of manufacturing alight-emitting device according to the present invention;

FIGS. 7A to 7C are diagrams showing a method of manufacturing alight-emitting device according to the present invention:

FIGS. 8A to 8C are diagrams of a light emitting device of the presentinvention before sealing with FIG. 8A showing the external thereof andFIGS. 8B and 8C showing an enlarged view and a sectional view of itsconnection portion at which the device is connected to an FPC;

FIGS. 9A and 9B are a diagram showing a light-emitting device of thepresent invention when it is bent and a sectional view thereof;

FIG. 10 is a sectional view of a light-emitting device of the presentinvention before sealing and shows its connection portion at which thedevice is connected to an FPC;

FIGS. 11A to 11D are diagrams showing a method of manufacturing alight-emitting device according to the present invention;

FIGS. 12A to 12C are diagrams showing a method of manufacturing alight-emitting device according to the present invention:

FIGS. 13A to 13C are diagrams showing a method of manufacturing TFTs andOLEDs of a light-emitting device according to the present invention;

FIGS. 14A to 14C are diagrams showing a method of manufacturing TFTs andOLEDs of a light-emitting device according to the present invention;

FIGS. 15A and 15B are diagrams showing a method of manufacturing TFTsand OLEDs of a light-emitting device according to the present invention;

FIG. 16 is a sectional view of a light-emitting device of the presentinvention;

FIG. 17 is a diagram illustrating how an adhesive layer is removed by awater jet method;

FIG. 18 is a diagram illustrating how an organic light emitting layer isformed by spraying;

FIGS. 19A and 19B are a top view of pixels and a circuit diagram ofpixels;

FIG. 20 is a diagram showing the circuit structure of a light-emittingdevice; and

FIGS. 21A to 21D are diagrams of electronic equipment that use alight-emitting device of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment Mode

First, an FPC 103 for supplying a voltage of a power supply and variouskinds of signals is mounted to an OLED panel 101 that has a plasticsubstrate. A drying agent 104 is provided for preventing the OLED frombeing degraded by oxygen, moisture, and the like. The drying agent 104is a hygroscopic substance (preferably barium oxide) or a substance thatcan adsorb oxygen. Here, the drying agent 104 is placed in a positionthat brings the drying agent to a contact with the FPC 103 and with anend face of the substrate 101. This prevents a sealing film and aplastic film from being locally stretched and broken in a later vacuumpress-fit step.

Next, the OLED panel 101 and the drying agent 104 are together put in abag-like plastic film 105. The inside of the bag-like plastic film islined with a sealing film 109 and the sealing film 109 acts as a gasbarrier. At this point, the portion at which the OLED panel 101 isconnected to the FPC 103 is placed inside the bag-like plastic film 105(FIG. 1A).

The sealing film 109 is composed of two or more layers of inorganicinsulating films and an organic insulating film that is interposedbetween the inorganic insulating films. The inorganic insulating filmsare insulating films of an inorganic material that can preventtransmission of moisture and oxygen. The organic insulating film is aninsulating film of an organic material that is smaller in internalstress than the material of the inorganic insulating films.

For example the sealing film 109 in this embodiment mode is an inorganicinsulating film 106 that is in contact with the plastic film 105, anorganic insulating film 107 that is in contact with the inorganicinsulating film 106, and an inorganic insulating film 108 that is incontact with the organic insulating film 107.

It is sufficient that at least two layers of inorganic insulating filmsare provided. Examples of the usable inorganic insulating films includea silicon nitride film, a silicon oxynitride film, an aluminum oxidefilm, an aluminum nitride film, an aluminum oxynitride film, and analuminum silicon oxynitride film (AlSiON). An aluminum siliconoxynitride film has relatively high heat conductivity and therefore canefficiently release heat generated in the element when used for theinorganic insulating films.

The inorganic insulating films are desirably 50 nm to 3 μm in thickness.The method of forming the inorganic insulating films is not limited toonly plasma CVD, but can be chosen to suit individual cases. Forinstance, LPCVD, sputtering or the like may be employed to form theinorganic insulating films.

The material used for the organic insulating film has to be one which istransmissive of light, which can make the internal stress of the organicinsulating film smaller than that of the inorganic insulating films, andwhich gives the organic insulating film a heat resistance high enough towithstand heat treatment in a later step. Typical examples of theorganic insulating film material include polyimide acrylic, polyamide,polyimideamide, benzocyclobutene, and an epoxy resin. Other resins thanthose given in the above may be used.

The organic insulating film is desirably 200 nm to 2 μm in thickness.

The bag-like plastic film 105 is exhausted until it reaches vacuum andthen the mouth of the plastic film is sealed by an adhesive 102. TheOLED panel 101 is thus sealed in the bag-like plastic film 105 whilesurrounded by the sealing film 109. The FPC 103 partially sticks out ofthe bag-like plastic film 105 in order to supply a voltage of a powersupply and various kinds of signals.

FIG. 1B shows a sectional view of the light-emitting device after thevacuum press-fitting and FIG. 1C shows a top view thereof. FIG. 1Bcorresponds to the sectional view taken along the line A-A′ in FIG. 1C.The plastic film 105 and the sealing film 109 have to be transparent ortranslucent to visible light. The plastic film 105 can use any materialas long as it is suitable for vacuum press-fitting.

This embodiment uses an adhesive to seal the plastic film.Alternatively, the inside of the plastic film may have partially aregion that is not lined with the sealing film so that the plastic filmis sealed by thermal press-fitting at this region. After the thermalpress-fitting, an adhesive may be used in the press-fit portion in orderto enhance the sealing. The film material is preferably one that is alsobonded to a flexible tape of the FPC during the thermal press-fitting.

The material of the plastic film is a thermoplastic resin material(polyester, polypropylene, polyvinyl chloride, polyvinyl fluoride,polystyrene, polyacrylonitrile, polyethylene terephthalate, nylon,etc.). Typically, a PVF (polyvinyl fluoride) film, a Mylar film, or anacrylic resin film is used.

The plastic film used here is shaped like a bag or box. Alternatively,the plastic film may be two sheets which are superposed on one anotherand sealed on four sides by an adhesive or thermal press-fitting.

Desirably, the above steps are carried out after the OLED is formed onthe substrate while avoiding exposure of the OLED to the outside air asmuch as possible.

In this way the present invention provides a light-emitting device withan OLED formed on a substrate in which degradation by moisture, oxygenand the like is reduced to improve the reliability.

Embodiments of the present invention will be described below.

Embodiment 1

A method of forming a sealing film in a bag-like plastic film will bedescribed in this embodiment.

FIG. 2 shows the structure of apparatus for forming a sealing film byplasma CVD. An electrode 203 connected to an RF power supply 202 and anelectrode 204 grounded are provided in a chamber 201.

The electrode 203 is placed so as to cover the outside of a bag-likeplastic film 205. The electrode 204 is placed inside the bag-likeplastic film 205. It is essential that the distance between theelectrode 203 and the plastic film 205 and the distance between theelectrode 204 and the plastic film 205 are set such that a sealing filmis positively formed on the inside of the plastic film 205 than on theoutside. Specifically, the distance between the electrode 203 and theplastic film 205 is set longer than the distance between the electrode204 and the plastic film 205. Desirably, the distance between theelectrode 203 and the plastic film 205 is equal to or more than 3 mm,more desirably, equal to or more than 10 mm.

The plastic film 205 is held by a holder 206 to a fixed position. Theholder 206 is structured so as to prevent the mouth of the bag-likeplastic film 205 from closing.

If the inside of the plastic film 205 is closely in contact with theholder 206 partially during formation of the sealing film, a regionwhere the sealing film is not formed and the plastic film is exposed canbe formed on the inside of the plastic film 205. At the region where theplastic film is exposed, the plastic film is press-fit thermally whenthe OLED panel is sealed by thermal press-fitting.

This embodiment describes a case of forming, on the inside of theplastic film 205, a sealing film 208 composed of two or more layers ofinorganic insulating films and an organic insulating film that isinterposed between the inorganic insulating films.

The inorganic insulating films used are insulating films which containan inorganic material and which are capable of preventing transmissionof oxygen and moisture. The organic insulating film used is aninsulating film which contains an organic material having internalstress smaller than that of the inorganic insulating films.Specifically, this embodiment uses a silicon oxynitride film for aninorganic insulating film 209, a polyethylene film for an organicinsulating film 210, and a silicon oxynitride film for an inorganicinsulating film 211. The inorganic insulating film 209 is in contactwith the plastic film 205 formed of PET. The organic insulating film 210is in contact with the inorganic insulating film 209. The inorganicinsulating film 211 is in contact with the organic insulating film 210.

The materials of the plastic film and the inorganic insulating films arenot limited to the ones given in the above. The materials of the plasticfilm and the inorganic insulating films can be chosen freely from thematerials listed in Embodiment Mode. However, this embodiment employsplasma CVD to form the sealing film and therefore materials that can beformed into films by plasma CVD should be used for the inorganicinsulating films.

The material of the organic insulating film is not limited topolyethylene. The material that can be used for the organic insulatingfilm has to be capable of forming an organic insulating film that istransmissive of light, smaller in internal stress than the inorganicinsulating films, and can withstand heat treatment in a later step.However, this embodiment employs plasma CVD to form the sealing film andtherefore it is essential that the material of the organic insulatingfilm has to be one that can be formed into a film by plasma CVD.Examples of the usable organic insulating film material includepolyethylene, polytetrafluoroethylene, polystyrene, benzocyclobutene,poly(p-phenylene vinylene), polyvinyl chloride, and apolyparaxylene-based resin.

First, the chamber 201 is exhausted till it reaches vacuum. Then, SiH₄,NH₃, and N₂O are introduced as reaction gas into the chamber 201 and asilicon oxynitride film is formed as the inorganic insulating film 209by plasma CVD.

Next, the chamber 201 is again exhausted till it reaches vacuum andethylene is introduced as reaction gas into the chamber 201 to form apolyethylene film as the organic insulating film 210 by plasma CVD.

After the chamber 201 is exhausted till it reaches vacuum once more,SiH₄, NH₃, and N₂O are introduced as reaction gas into the chamber 201and a silicon oxynitride film is formed as the inorganic insulating film211 by plasma CVD.

If a protective insulating film 207 is formed on the inner wall of thechamber 201 in advance, deposition of the sealing film materials on theinner wall can be avoided and most of the materials can be formed intothe sealing film 208 on the plastic film 205.

This embodiment employs plasma CVD to form the sealing film 208, but themethod of forming the sealing film is not limited thereto. For instance,thermal CVD, evaporation, sputtering, or low pressure thermal CVD can beused to form the sealing film.

Embodiment 2

A method of sealing an OLED panel using a plastic film will be describedin this embodiment.

FIGS. 3A to 3C show the structure of apparatus for sealing an OLED panelin a bag-like plastic film (sealing apparatus). The sealing apparatushas two chambers, namely, a chamber A 302 and a chamber B 303, which areseparated from each other by a partition film 301. The partition film301 has elasticity and includes property of generating a force forcorrecting deformation even when it is distorted by an external force.

The chamber A 302 and the chamber B 303 each have an exhaust system. Thechamber B 303 has a heater 304 and a cooler 305.

First, as shown in FIG. 3A, an OLED panel 307 is put in a bag-likeplastic film 306 and the plastic film is placed in the chamber B 303. Atthis point, the OLED panel 307 has an FPC 310 mounted thereto and anadhesive 308 is placed near the mouth of the bag-like plastic film 306.

Next, the chamber A 302 and the chamber B 303 are exhausted until theyreach vacuum and inert gas (Ar, in this embodiment) is then introducedto the chamber B 303. The chamber is again exhausted till it reachesvacuum to remove oxygen and moisture in the chamber B 303.

The heater 304 is used to melt the adhesive 308. The adhesive 308 usedin this embodiment is a hot melt adhesive that obtains adhesion whenheated and melted. Typically, a hot melt adhesive using as the baseethylene-vinyl acetate copolymer, or polyamide, or polyester isemployed.

While the adhesive 308 is melted by heat, the pressure in the chamber A302 is increased by exposure to the air or other measures. This causesthe chamber A 302 to depress the chamber B 303 as shown in FIG. 3B. As aresult, the elastic partition film 301 presses the plastic film 306. Themelted adhesive 308 is also pressed to seal the OLED panel 307 in vacuumin the bag-like plastic film 306.

In this state, the adhesive 308 is cooled by the cooler 305. Theadhesive 308 is thus solidified with the OLED panel 307 sealed in vacuumin the bag-like plastic film 306.

Next, as shown in FIG. 3C, the pressure in the chamber B 303 isincreased to put a distance between the partition film 301 and thesealed OLED panel 307.

The OLED panel 307 can be sealed in vacuum in the bag-like plastic filmby the method described above.

The method of sealing the OLED panel is not limited to the one shown inthis embodiment.

This embodiment may be freely combined with Embodiment 1.

Embodiment 3

In this Embodiment, fabrication method of OLED panel in which includesOLED formed on the plastic substrate is described. FIGS. 4 and 5 is thecross sectional view of fabrication steps of pixel portion and drivingcircuit.

In FIG. 4A, a first bonding layer 1102 made of an amorphous silicon filmis formed to have a thickness of 100 to 500 nm (300 nm in thisembodiment) on a first substrate 1101. Although a glass substrate isused as the first substrate 1101 in this embodiment, a quartz substrate,a silicon substrate, a metal substrate or a ceramic substrate may bealternatively used. Any material can be used for the first substrate1101 as long as it is resistant to a treatment temperature in the latermanufacturing steps.

As a method of forming the first bonding layer 1102, a low pressurethermal CVD method, a plasma CVD method, a sputtering method or anevaporation method may be used. On the first bonding layer 1102, aninsulating film 1103 made of a silicon oxide film is formed to have athickness of 200 nm. As a method of forming the insulating film 1103, alow pressure thermal CVD method, a plasma CVD method, a sputteringmethod or an evaporation method may be used. The insulating film 1103serves to protect an element formed on the first substrate 1101 when thefirst bonding layer 1102 is removed to peel off the first substrate1101.

Next, an element is formed on the insulating film 1103 (FIG. 4B). Theelement herein designates a semiconductor element (typically, a TFT) oran MIM element, which is used as a switching element for a pixel, anOLED and the like in the case of an active matrix light-emitting device.In the case of a passive light-emitting device, the element designatesan OLED. In FIG. 4B, a TFT 1104 a in a driving circuit 1106. TFTs 1104 band 1104 c and an OLED 1105 in a pixel portion 1107 are shown asrepresentative elements.

Then, an insulating film 1108 is formed so as to cover theabove-described elements. It is preferred that the insulating film 1108has a flatter surface after its formation. It is not necessarilyrequired to provide the insulating film 1108.

Next, as shown in FIG. 4C, a second substrate 1110 is bonded through asecond bonding layer 1109. In this embodiment, a plastic substrate isused as the second substrate 1110. More specifically, a resin substratehaving a thickness of 10 μm or more, for example, a substrate made ofPES (polyether sulfone), PC (polycarbonate), PET (polyethyleneterephthalate) or PEN (polyethylene naphthalate) can be used.

As a material of the second bonding layer 1109, it is necessary to usesuch a material that can provide a high selection ratio when the firstbonding layer 1102 is to be removed in the later step. Typically, aninsulating film made of a resin can be used as the second bonding layer1109. Although polyimide is used as a material of the second bondinglayer 1109 in this embodiment mode, acryl, polyamide or an epoxy resincan be alternatively used. In the case where the second bonding layer1109 is placed on the viewer side (the side of a light-emitting deviceuser) when seen from the OLED, a material is required to have lighttransmittance.

Next, as shown in FIG. 5A, the first substrate 1101, the secondsubstrate 1110 and all the elements and the entire films formedtherebetween are exposed to a gas containing halogen fluoride so as toremove the first bonding layer 1102. In this embodiment, chlorinetrifluoride (ClF₃) is used as halogen fluoride, and nitrogen is used asa diluent gas. Alternatively, argon, helium or neon may be used as adiluent gas. A flow rate may be set to 500 sccm (8.35×10⁻⁶ m³/s) forboth gases, and a reaction pressure may be set to 1 to 10 Torr (1.3×10²to 1.3×10³ Pa). A treatment temperature may be a room temperature(typically, 20 to 27° C.).

In this case, the silicon film is etched whereas the plastic film, theglass substrate, the polyimide film, and the silicon oxide film are notetched. More specifically, through exposure to chlorine trifluoride, thefirst bonding layer 1102 is selectively etched to result in completeremoval thereof. Since an active layer of the TFT, which is similarlymade of a silicon layer, is not exposed to the outside, the active layeris not exposed to chlorine trifluoride and therefore is not etched.

In this embodiment mode, the first bonding layer 1102 is graduallyetched from its exposed edge portions. The first substrate 1101 and theinsulating film 1103 are separated from each other when the firstbonding layer 1102 is completely removed. The TFTs and the OLED, each ofwhich includes a laminate of thin films, remain on the second substrate1110.

A large-sized substrate is not preferred as the first substrate 1101because the etching gradually proceeds from the edges of the firstbonding layer 1102 and therefore the time required for completelyremoving the first bonding layer 1102 gets long with increase in size.Therefore, it is desirable that this embodiment mode is carried out forthe first substrate 1101 having a diagonal of 3 inches or less(preferably, 1 inch or less).

After the peeling of the first substrate 1101 in this manner, a thirdbonding layer 1113 is formed as shown in FIG. 5B. Then, a thirdsubstrate 1112 is bonded through the third bonding layer 1113. In thisembodiment, a plastic substrate is used as the third substrate 1110.More specifically, a resin substrate having a thickness of 10 μm ormore, for example, a substrate made of PES (polyether sulfone), PC(polycarbonate), PET (polyethylene terephthalate) or PEN (polyethylenenaphthalate) can be used as the third substrate.

As the third bonding layer 1113, an insulating film made of a resin(typically, polyimide, acryl, polyamide or an epoxy resin) can be used.In the case where the third bonding layer 1113 is placed on the viewerside (the side of a light-emitting device user) when seen from the OLED,a material is required to have light transmittance.

In this manner, a flexible OLED panel (light-emitting device) interposedbetween the two flexible substrates 1110 and 1112 having flexibility canbe obtained. With use of the same material for the second substrate 1110and the third substrate 1112, the substrates 1110 and 1112 have the samethermal expansion coefficient. As a result, the substrates 1110 and 1112can be hardly affected by a stress strain due to change in temperature.

Next, as shown in FIG. 5C, OLED panel is sealed with a plastic film 1118on which a sealing film 1119 is formed. At that time, the sealing film1119 is placed between the plastic film 1118 and OLED 1105.

In this embodiment, as the sealing film 1119, inorganic insulating film1119 a, organic insulating film 1119 b, inorganic insulating film 1119 care formed with the order near the plastic film 1118.

The light-emitting device manufactured according to this embodimentallows the manufacture of an element using a semiconductor (for example,a TFT) without being limited by a heat resistance of the plasticsubstrate. Thus, the light-emitting device having extremely highperformance can be obtained.

Although the first bonding layer 1102 is made of amorphous silicon andis removed with a gas containing halogen fluoride in this embodiment thepresent invention, is not limited to this structure. A material and aremoval method of the first bonding layer 1102 can be suitablydetermined by those who carry out the invention. It is important todetermine a material and a removal method of the first bonding layer sothat the substrates, the elements and the films other than the firstbonding layer, which are not desired to be removed, are not removed withremoval of the first bonding layer so as not to affect the operation ofthe light-emitting device. It is also important that a material of thefirst bonding layer does not allow its removal in the process other thanin the removal step of the first bonding layer.

For example, an organic material, which is entirely or partiallyvaporized by radiation of a laser beam, can be used as the first bondinglayer. Additionally it is desirable that a material having laser beamabsorbance, for example, a colored or black material (for example, aresin material containing a black colorant) is used so that a laser beamis efficiently absorbed only by the first bonding layer in the casewhere a second harmonic wave from a YAG laser is used. A material, whichis not vaporized in a heat treatment in the element formation steps, isused for the first bonding layer.

Each of the first, second and third bonding layers may be eithersingle-layered or multi-layered. An amorphous silicon film or a DLC filmmay be provided between the bonding layer and the substrate.

The first bonding layer may be formed of an amorphous silicon film, andthe first substrate may be peeled off by radiation of a laser beam ontothe first bonding layer in the later step. In this case, in order tofacilitate the peeling of the first substrate, it is preferred to use anamorphous silicon film containing a large amount of hydrogen. Hydrogencontained in the amorphous silicon film is vaporized by radiation of alaser beam, so that the first substrate can be easily peeled off.

As a laser beam, a pulse oscillation or a continuous wave excimer laser,a YAG laser or a YVO₄ laser can be used. A laser beam is radiated ontothe first bonding layer through the first substrate so as to vaporizeonly the first bonding layer to peel off the first substrate. Therefore,as the first substrate, it is preferred to use a substrate through whichat least a radiated laser beam is allowed to pass, typically a substratehaving light transmittance, for example, a glass substrate, a quartzsubstrate or the like, which has a thickness larger than those of thesecond and third substrates.

In the present invention, in order to allow a laser beam to pass throughthe first substrate, it is necessary to suitably select the type of alaser beam and the first substrate. For example, when a quartz substrateis used as the first substrate, a YAG laser (fundamental wave (1064 nm),a second harmonic wave (532 nm), a third harmonic wave (355 nm), and afourth harmonic wave (266 nm)) or an excimer laser (wavelength: 308 nm)is used to form a linear beam which is in turn allowed to pass throughthe quartz substrate. It is noticed that an excimer laser beam does notpass through a glass substrate. Therefore, when a glass substrate isused as the first substrate, a fundamental wave, a second harmonic waveor a third harmonic wave of the YAG laser, preferably, a second harmonicwave (wavelength: 532 nm), is used to form a linear beam which is inturn allowed to pass through the glass substrate.

Alternatively, for example, a method of separating the first substrateby spraying a fluid (a pressure-applied liquid or gas) on the firstbonding layer (typically, a water jet method) may be used.

In the case where the first bonding layer is made of an amorphoussilicon film, the first bonding layer may be removed by using hydrazine.

Alternatively, a method of separating the first substrate by etching,described in a U.S. Pat. No. 5,821,138 may be employed. Specifically, anapplied silicon oxide film (SOG) may be used as the first bonding layerwhich is then removed by hydrogen fluoride. In this case, it isimportant that the silicon oxide film, which is not desired to beremoved, is formed to have a fine structure through a sputtering or aCVD method so that the silicon oxide film provides a high selectionratio when the first bonding layer is to be removed by hydrogenfluoride.

With such a structure, even if substrates having an extremely smallthickness, specifically, 50 to 300 μm, preferably 150 to 200 μm, areused as the second and third substrates, a light-emitting device withhigh reliability can be obtained. It was difficult to form an element onsuch a thin substrate by using a conventionally known manufactureapparatus. However, since the element is formed with being bonded ontothe first substrate, a manufacture apparatus using a thick substrate canbe used without any alteration of the apparatus.

With the use of the sealing film including the multi-layered insulatingfilm, it is possible to effectively restrain the degradation due topenetration of moisture or oxygen. Moreover, a crack is prevented fromoccurring upon bend of the substrate. As a result, a light-emittingdevice having enhanced flexibility can be realized.

Note that it is possible to implement Embodiment 3 in combination withEmbodiments 1 to 2.

Embodiment 4

In this Embodiment, different way from embodiment 3 of fabricationmethod of OLED panel in which includes OLED formed on the plasticsubstrate is described. FIGS. 6 and 7 is the cross sectional view offabrication steps of pixel portion and driving circuit.

In FIG. 6A, a first bonding layer 1202 made of an amorphous silicon filmis formed to have a thickness of 100 to 500 nm (300 nm in thisembodiment mode) is formed on a first substrate 1201. Although a glasssubstrate is used as the first substrate 1201 in this embodiment mode, aquartz substrate, a silicon substrate, a metal substrate or a ceramicsubstrate may be alternatively used. Any material can be used for thefirst substrate 1201 as long as it is resistant to a treatmenttemperature in the later manufacture steps.

As a method of forming the first bonding layer 1202, a low pressurethermal CVD method, a plasma CVD method, a sputtering method or anevaporation method may be used. On the first bonding layer 1202, aninsulating film 1203 made of a silicon oxide film is formed to have athickness of 200 nm. As a method of forming the insulating film 1203, alow pressure thermal CVD method, a plasma CVD method, a sputteringmethod or an evaporation method may be employed. The insulating film1203 serves to protect an element formed on the first substrate 1201when the first bonding layer 1202 is removed to peel off the firstsubstrate 1201.

Next, an element is formed on the insulating film 1203 (FIG. 6B). Theelement herein designates a semiconductor element (typically, a TFT) oran MIM element, which is used as a switching element for a pixel, and anOLED and the like in the case of an active matrix light-emitting device.In the case of a passive light-emitting device, the element designatesan OLED. In FIG. 6B, a TFT 1204 a in a driving circuit 1206, TFTs 1204 band 1204 c and an OLED 1205 in a pixel portion are shown asrepresentative elements.

Then, an insulating film 1208 is formed so as to cover theabove-described elements. It is preferred that the insulating film 1208has a flatter surface after its formation. It is not necessarilyrequired to provide the insulating film 1208.

Next, as shown in FIG. 6C, a second substrate 1210 is bonded to thefirst substrate 1201 through a second bonding layer 1209. Although aglass substrate is used as the second substrate 1210 in this embodimentmode, a quartz substrate, a silicon substrate, a metal substrate or aceramic substrate may also be used. Any material may be used for thesecond substrate 1210 as long as the material is resistant to atreatment temperature in the later manufacture step.

As a material of the second bonding layer 1209, it is necessary to use amaterial which can provide a high selection ratio when the first bondinglayer 1202 is to be removed in the later step. Furthermore, for thesecond bonding layer 1209, it is required to use such a material that athird bonding layer serving to bond a third substrate is not removedwith the removal of the second bonding layer and does not cause thepeeling of the third substrate. In this embodiment, a polyamic acidsolution which is a precursor of a polyimide resin, described inJapanese Patent Application Laid-open No. Hei 5-315630, is used.Specifically, after the second bonding layer 1209 is formed to have athickness of 10 to 15 μm using a polyamic acid solution, which is anuncured resin, the second substrate 1210 and the interlayer insulatingfilm 1208 are bonded to each other through thermocompression bonding.Then, heating is conducted so as to temporarily cure the resin.

In this embodiment, a material of the second bonding layer is notlimited to a polyamic acid solution. Any material may be used as long asit provides a high selection ratio when the first bonding layer 1202 isto be removed in the later step and the third bonding layer for bondingthe third substrate is not removed with the removal of the secondbonding layer and does not cause the peeling of the third substrate. Itis important that the second bonding layer is made of such a materialthat is not removed in the steps other than the step of removing thesecond bonding layer.

Next, as shown in FIG. 6D, the first substrate 1201, the secondsubstrate 1210 and all the elements and the entire films formedtherebetween are exposed to a gas containing halogen fluoride so as toremove the first bonding layer 1202. In this embodiment, chlorinetrifluoride (ClF₃) is used as halogen fluoride, and nitrogen is used asa diluent gas. Alternatively, argon, helium or neon may be used as adiluent gas. A flow rate for both gases may be set to 500 sccm(8.35×10⁻⁶ m³/s), and a reaction pressure may be set to 1 to 10 Torr(1.3×10² to 1.3×10³ Pa). A treatment temperature may be a roomtemperature (typically, 20 to 27° C.).

In this case, the silicon film is etched whereas the plastic film, theglass substrate, the polyimide film, and the silicon oxide film are notetched. More specifically, through exposure to a chlorine trifluoridegas, the first bonding layer 1202 is selectively etched to result incomplete removal thereof. Since an active layer of the TFT, which issimilarly made of a silicon film, is not exposed to the outside, theactive layer is not exposed to a chlorine trifluoride gas and thereforeis not etched.

In this embodiment, the first bonding layer 1202 is gradually etchedfrom its exposed edge portions. The first substrate 1201 and theinsulating film 1203 are separated from each other when the firstbonding layer 1202 is completely removed. After removal of the firstbonding layer 1202, the TFTs and the OLED, each of which includes alaminate of thin films, remain on the second substrate 1210.

A large substrate is not preferred as the first substrate 1201 becausethe first bonding layer 1202 is gradually etched from its edges and thetime required for completely removing the first bonding layer 1202 getslong with increase in size. Therefore, it is desirable that thisembodiment is carried out for the first substrate 1201 having a diagonalof 3 inches or less (preferably, 1 inch or less).

After removal of the first substrate 1201 in this manner, a thirdbonding layer 1213 is formed as shown in FIG. 7A. Then, a thirdsubstrate 1212 is bonded to the second substrate 1210 through the thirdbonding layer 1213. In this embodiment, a plastic substrate is used asthe third substrate 1210. More specifically, a resin substrate having athickness of 10 μm or more, for example, a substrate made of PES(polyether sulfone), PC (polycarbonate), PET (polyethyleneterephthalate) or PEN (polyethylene naphthalate) can be used as thethird substrate.

An insulating film made of a resin (typically, polyimide, acryl,polyamide or an epoxy resin) can be used as the third bonding layer1213. In the case where the third bonding layer 1213 is placed on theviewer side (the side of a light-emitting device user) when seen fromthe OLED, a material is required to have light transmittance.

Next, as shown in FIG. 7B, the second bonding layer 1209 is removed topeel off the second substrate 1210. More specifically, the secondbonding layer 1209 is removed by being dipped into water for about anhour, thereby allowing the second substrate 1210 to be peeled off.

It is important to select a method of peeling off the second bondinglayer 1209 according to a material of the second bonding layer, amaterial of the element or the films, a material of the substrate, andthe like.

In this manner, a flexible OLED panel (light-emitting device) using asingle plastic substrate 1212 can be obtained.

Next, as shown in FIG. 7C, OLED panel is sealed with a plastic film 1218on which a sealing film 1219 is formed. At that time, the sealing film1219 is placed between the plastic film 1218 and OLED 1205.

In this embodiment, as the sealing film 1219, inorganic insulating film1219 a, organic insulating film 1219 b, inorganic insulating film 1219 care formed with the order near the plastic film 1218.

Since an element using a semiconductor (for example, a TFT) can beformed without being limited by a heat resistance of the plasticsubstrate, the light-emitting device having extremely high performancecan be manufactured according to this embodiment.

Although the first bonding layer 1202 is made of amorphous silicon, andis removed with a gas containing halogen fluoride in this embodiment,the present invention is not limited to this structure. A material and aremoval method of the first bonding layer can be suitably determined bythose who carry out the invention. It is important to determine amaterial and a removal method of the first bonding layer so that thesubstrates, the other bonding layers, the elements and the films otherthan the first bonding layer, which are not desired to be removed, arenot removed with removal of the first bonding layer so as not to affectthe operation of the light-emitting device. It is also important that amaterial of the first bonding layer does not allow its removal in theprocess other than the removal step of the first bonding layer.

Although a polyamic acid solution, which is a precursor of a polyimideresin, is used for the second bonding layer 1209 which is then removedwith water, the structure of the present invention is not limitedthereto. A material and a removal method of the second bonding layer canbe suitably determined by those who carry out the invention. It isimportant to determine a material and a removal method of the secondbonding layer so that the substrates, the other bonding layers, theelements and the films other than the second bonding layer, which arenot desired to be removed, are not removed with removal of the secondbonding layer so as not to affect the operation of the light-emittingdevice. It is also important that a material of the second bonding layerdoes not allow its removal in the process other than the removal step ofthe second bonding layer.

For example, an organic material, which is entirely or partiallyvaporized by radiation of a laser beam, can be used for the first andsecond bonding layers. Additionally, it is desirable that a materialhaving laser beam absorbance, for example, a colored or black material(for example, a resin material containing a black colorant) is used sothat a laser beam is efficiently absorbed only by the first and secondbonding layers in the case where a second harmonic wave from a YAG laseris used. The first and second bonding layers, which are not vaporized ina heat treatment in the element formation steps, are employed.

Each of the first, second and third bonding layers may be eithersingle-layered or multi-layered. An amorphous silicon film or a DLC filmmay be provided between the bonding layer and the substrate.

The first bonding layer or the second bonding layer may be formed of anamorphous silicon film, and the substrate may be peeled off by radiationof a laser beam onto the first bonding layer or the second bonding layerin the later step. In this case, in order to facilitate the peeling ofthe first substrate, it is preferred to use an amorphous silicon filmcontaining a large amount of hydrogen. Hydrogen contained in theamorphous silicon film is vaporized by radiation of a laser beam, sothat the substrate can be easily peeled off.

As a laser beam, a pulse oscillation or a continuous wave excimer laser,a YAG laser or a YVO₄ laser can be used. In the case where the firstsubstrate is to be peeled off, a laser beam is radiated onto the firstbonding layer through the first substrate so as to vaporize only thefirst bonding layer to peel off the first substrate. In the case wherethe second substrate is to be peeled off, a laser beam is radiated ontothe second bonding layer through the second substrate so as to vaporizeonly the second bonding layer to peel off the second substrate.Therefore, as the first or second substrate, it is preferred to use asubstrate having a thickness larger than that of the third substrates,which allows at least a radiated laser beam to pass through, typically asubstrate having light transmittance, for example, a glass substrate, aquartz substrate or the like.

In the present invention, in order to allow a laser beam to pass throughthe first or second substrate, it is necessary to suitably select thetype of a laser beam and the type of the first substrate. For example,when a quartz substrate is used as the first substrate, a YAG laser(fundamental wave (1064 nm), a second harmonic wave (532 nm), a thirdharmonic wave (355 nm), and a fourth harmonic wave (266 nm)) or anexcimer laser (wavelength: 308 nm) is used to form a linear beam whichis in turn allowed to pass through the quartz substrate. It is noticedthat an excimer laser beam does not passes through a glass substrate.Therefore, when a glass substrate is used, a fundamental wave, a secondharmonic wave or a third harmonic wave of the YAG laser, preferably, asecond harmonic wave (wavelength: 532 nm), is used to form a linear beamwhich is in turn allowed to pass through the glass substrate.

Alternatively, for example, a method of separating the first substrateby spraying a fluid (a pressure-applied liquid or gas) on the firstbonding layer (typically, a water jet method) may be used.

In the case where the first bonding layer is made of an amorphoussilicon film, the first bonding layer may be removed by using hydrazine.

Alternatively, a method of separating the first substrate by etching,described in a U.S. Pat. No. 5,821,138 may be used. Specifically, anapplied silicon oxide film (SOG) may be used as the first or secondbonding layer which is then removed by hydrogen fluoride. In this case,it is important that the silicon oxide film, which is not desired to beremoved, is formed to have a fine structure through a sputtering or aCVD method so that the silicon oxide film provides a high selectionratio when the first or second bonding layer is to be removed byhydrogen fluoride.

With such a structure, even if a substrate having an extremely smallthickness, specifically, 50 to 300 μm, preferably 150 to 200 μm is usedas the third substrate, a light-emitting device with high reliabilitycan be obtained. It is difficult to form an element on such a thinsubstrate by using a conventionally known manufacture apparatus.However, since the element is formed with being bonded onto the firstand second substrates, a manufacturing apparatus using a thick substratecan be used without any alteration of the apparatus.

With the use of the sealing film including the multi-layered insulatingfilm it is possible to effectively restrain the degradation due topenetration of moisture or oxygen. Moreover, a crack is prevented fromoccurring upon bend of the substrate. As a result, a light-emittingdevice having enhanced flexibility can be realized.

In the first and second embodiment, either an anode or a cathode of theOLED may be used as a pixel electrode.

Note that it is possible to implement Embodiment 4 in combination withEmbodiments 1 to 2.

Embodiment 5

In Embodiment 5, the outward appearance of a light-emitting deviceaccording to the present invention and its connection to an FPC will bedescribed.

FIG. 8A shows an example of a top view of a light-emitting deviceaccording to the present invention, described in Embodiment 3. A secondsubstrate 1301 and a third substrate 1302 are both plastic substrateshaving flexibility. A pixel portion 1303 and driving circuits (asource-side driving circuit 1304 and a gate-side driving circuit 1305)are provided between the second substrate 1301 and the third substrate1302.

In FIG. 8A, there is shown an example where the source-side drivingcircuit 1304 and the gate side-driving circuit 1305 are formed on thesubstrate on which the pixel portion 1303 is also formed. However, thedriving circuits represented by the source-side driving circuit 1304 andthe gate side-driving circuit 1305 may be formed on a differentsubstrate from the substrate on which the pixel portion 1303 is formed.In this case, the driving circuits may be connected to the pixel portion1303 via an FPC or the like.

The number and the arrangement of the source-side driving circuit 1304and the gate-side driving circuit 1305 are not limited to the structureshown in FIG. 8A.

The reference symbol 1306 designates an FPC, via which a signal from anIC including a controller or a source voltage are supplied to the pixelportion 1303, the source-side driving circuit 1304 and the gate-sidedriving circuit 1305.

FIG. 8B is an enlarged view of a portion surrounded by a dot line inFIG. 8A where the FPC 1306 and the second substrate 1301 are connectedto each other. FIG. 8C is a cross-sectional view taken along a line A-A′in FIG. 8B.

Wirings 1310, which are extended so as to supply a signal or a sourcevoltage to the pixel portion 1303, the source-side driving circuit 1304and the gate-side driving circuit 1305, are provided between the secondsubstrate 1301 and the third substrate 1302. Terminals 1311 are providedfor the FPC 1306.

Note that 1314 designates the drying material and have the effect toprevent entering the material such as an oxygen or water, which helpdeterioration, to OLED (not shown).

The second substrate 1301 and various films such as an insulating filmprovided between the second substrate 1301 and the extended wirings 1310are partially removed by a laser beam or the like to provide contactholes 1313. Therefore, a plurality of the extended wirings 1310 areexposed through the contact holes 1313, and are respectively connectedto the terminals 1311 through a conductive resin 1312 having anisotropy.

Although there is shown the example where the extended wirings arepartially exposed from the side of the second substrate 1301 in FIGS. 8Ato 8C, the present invention is not limited thereto. Alternatively, theextended wirings may be partially exposed from the side of the thirdsubstrate 1302.

FIG. 9A shows the light-emitting device shown in FIG. 8A in a bentstate. Since the second substrate and the third substrate of the lightemitting device described in Embodiment 3 both have flexibility, thelight emitting device can be bent to a certain degree as shown in FIG.9A. Thus, such a light-emitting device has a wide range of applicationsbecause it can be used for a display having a curved surface, a showwindow and the like. Moreover, not only the light-emitting devicedescribed in Embodiment 3 but also the light-emitting device describedin Embodiment 4 can be similarly bent.

FIG. 9B is a cross-sectional view of the light-emitting device shown inFIG. 9A. A plurality of elements are formed between the second substrate1301 and the third substrate 1302. Herein, TFTs 1320 a, 1320 b and 1320c and an OLED 1322 are representatively shown. A broken line 1323represents a center line between the second substrate 1301 and the thirdsubstrate 1302.

The second substrate 1301 is covered with plastic film 1324 through thesealing film 1321. The third substrate 1302 is also covered with plasticfilm 1324 through the sealing film 1321.

The sealing film 1321 including a inorganic insulating film 1321 a whichcontact to plastic film 1324, an organic insulating film 1321 b whichcontact to inorganic insulating film 1321 a and inorganic insulatingfilm 1321 c which contact to organic insulating film 1321 b.

Next, the connection of the light-emitting device described inEmbodiment 4 to the FPC will be described. FIG. 10 is a cross-sectionalview showing a portion where the light-emitting device described inEmbodiment 4 and the FPC are connected to each other.

A wiring 1403 for extension is provided on a third substrate 1401.

Various films such as an insulating film provided between the thirdsubstrate 1401 and the extended wring 1403 are partially removed by alaser beam or the like to provide a contact hole. Therefore, theextended wiring 1403 is exposed through the contact hole, and iselectrically connected to a terminal 1405 included in an FPC 1404through a conductive resin 1406 having anisotropy.

Although there is shown the example where the extended wiring 1403 ispartially exposed by removing the part of insulating film provided onthe extended wiring 1403 in FIG. 10, the present invention is notlimited thereto. Alternatively, the extended wiring 1403 may bepartially exposed from the side of the third substrate 1401.

Note that it is possible to implement Embodiment 5 in combination withEmbodiments 1 to 2.

Embodiment 6

In Embodiment 6, an example of manufacturing method of thelight-emitting device of the present invention is explained.

In FIG. 11A, a first bonding layer 502 made of an applied silicon oxidefilm (SOG) is formed to have a thickness of 100 to 500 nm (300 nm inthis embodiment) is formed on a first substrate 501. Although a glasssubstrate is used as the first substrate 501 in this embodiment, aquartz substrate, a silicon substrate, a metal substrate or a ceramicsubstrate may be alternatively used. Any material can be used for thefirst substrate 501 as long as it is resistant to a treatmenttemperature in the later manufacturing steps.

As a method of forming the SOG film, an iodine solution is added to anSOG solution by spin coating, which is then dried to desorb iodinetherefrom. Then, a thermal treatment at about 400° C. is conducted toform the SOG film. In this embodiment, the SOG film having a thicknessof 100 nm is formed. A method of forming the SOG film as the firstbonding layer 502 is not limited to the above method. Both an organicSOG and an inorganic SOG may be used as the SOG; any SOG can be used aslong as it can be removed with hydrogen fluoride in the later step. Itis important that the silicon oxide film, which is not desired to beremoved, is formed to have a fine structure by sputtering or a CVDmethod so as to provide a high selection ratio when the first bondinglayer is to be removed with hydrogen fluoride.

Next, a protection film made of Al is formed on the first bonding layer502 by a low pressure thermal CVD method, a plasma CVD method, asputtering method or an evaporation method. In this embodiment, aprotection film 503 made of Al is formed to have a thickness of 200 nmon the first bonding layer 502 by sputtering.

Although Al is used as a material of the protection film 503 in thisembodiment, the present invention is not limited thereto. It isimportant to select such a material that is not removed with removal ofthe first bonding layer 502 and that is not removed in the process otherthan in the step of removing the protection film 503. Furthermore, it isimportant that such a material does not allow removal of the other filmsand the substrates in the step of removing the protection film 503. Theprotection film 503 serves to protect an element formed on the firstsubstrate 501 when the first bonding layer 502 is removed to peel offthe first substrate 501.

Next, an element is formed on the protection film 503 (FIG. 11B). InFIG. 11B, TFTs 504 a and 504 b in a driving circuit are shown asrepresentative elements.

In this embodiment, the TFT 504 a is an n-channel TFT whereas the TFT504 b is a p-channel TFT. The TFTs 504 a and 504 b form a CMOS.

The TFT 504 a includes a first electrode 550 formed on the protectionfilm 503, an insulating film 551 formed so as to cover the firstelectrode 550, a semiconductor film 552 formed so as to be in contactwith the insulating film 551, an insulating film 553 formed so as to bein contact with the semiconductor film 552, and a second electrode 554in contact with the insulating film 553.

The TFT 504 b includes a first electrode 560, the insulating film 551formed so as to cover the first electrode 560, a semiconductor film 562formed so as to be in contact with the insulating film 551, theinsulating film 553 formed so as to be in contact with the semiconductorfilm 562, and a second electrode 564 in contact with the insulating film553.

A terminal 570, which is formed simultaneously with the first electrodes550 and 560, is provided on the protection film 503.

Then, an insulating film 565 is formed so as to cover the TFTs 504 a and504 b. A wiring 571 being in contact with the semiconductor film 55′ andthe terminal 570, a wiring 572 being in contact with the semiconductorfilms 552 and 562, and a wiring 573 being in contact with thesemiconductor film 562 are formed via contact holes formed through theinsulating films 565, 551 and 553.

Although not shown, an OLED is formed on the insulating film 565. Aninsulating film 574 is formed so as to cover the wirings 571, 572 and573, the insulating film 565 and the OLED. It is preferred that theinsulating film 574 has a flatter surface after its formation. Theinsulating film 574 is not necessarily formed.

Next, as shown in FIG. 11C, a second substrate 510 is bonded to thefirst substrate through a second bonding layer 509. A plastic substrateis used as the second substrate 510 in this embodiment. Morespecifically a resin substrate having a thickness of 10 μm or more, forexample, a substrate made of PES (polyether sulfone), PC(polycarbonate), PET (polyethylene terephthalate) or PEN (polyethylenenaphthalate) can be used as the second substrate 510.

As a material of the second bonding layer 509, it is necessary to use amaterial which can provide a high selection ratio when the first bondinglayer 502 is to be removed in the later step. Typically, an insulatingfilm made of a resin can be used. Although polyimide is used in thisembodiment, acryl, polyamide or an epoxy resin can also be used. In thecase where the second bonding layer 509 is placed on the viewer side(the side of a light-emitting device user) when seen from the OLED, amaterial is required to have light transmittance.

Next, as shown in FIG. 11D, the first bonding layer 502 is removed withhydrogen fluoride. In this embodiment, the first and second substrates501 and 510, and all the elements and the entire films formedtherebetween are dipped into buffered hydrofluoric acid (HF/NH₄F=0.01 to0.2, for example, 0.1) so as to remove the first bonding layer 502.

Since the silicon oxide film, which is not desired to be removed, ismade of a fine film formed by sputtering or a CVD method, only the firstbonding layer is removed with hydrogen fluoride.

In the case of this embodiment, the first bonding layer 502 is graduallyetched from its exposed edge portions. The first substrate 501 and theprotection film 503 are separated from each other when the first bondinglayer 502 is completely removed. After removal of the first bondinglayer 502, the TFTs and the OLED, each of which includes a laminate ofthin films, remain on the second substrate 510.

A large substrate is not preferred as the first substrate 501 becausethe time required for completely removing the first bonding layer 502from its edges gets long with increase in size of the first substrate.Therefore, it is desirable that this embodiment is carried out for thefirst substrate 501 having a diagonal of 3 inches or less (preferably, 1inch or less).

Next, as shown in FIG. 12A, the protection film 503 is removed. In thisembodiment, the protection film 503 made of Al is removed by wet etchingwith a phosphoric acid type etchant so as to expose the terminal 570 andthe first electrodes 550 and 560.

Then, as shown in FIG. 12B, a third bonding layer 513 made of aconductive resin having anisotropy is formed. Through the third bondinglayer 513, the third substrate 512 is attached to the side where theterminal 570 and the first electrodes 550 and 560 are exposed.

In this embodiment, a plastic substrate is used as the third substrate512. More specifically, a resin substrate having a thickness of 10 μm ormore, for example, a substrate made of PES (polyether sulfone), PC(polycarbonate), PET (polyethylene terephthalate) or PEN (polyethylenenaphthalate) can be used as the third substrate 512.

As the third bonding layer 513, an insulating film made of a resin(typically, polyimide, acryl, polyamide or an epoxy resin) can be used.In the case where the third bonding layer 513 is placed on the viewerside when seen from the OLED, a material is required to have lighttransmittance.

Then, a contact hole is formed through the third substrate 512 by alaser beam or the like. Al is evaporated on a portion of the thirdsubstrate 512 where the contact hole is formed and the peripherythereof, thereby forming terminals 580 and 581 on the respectivesurfaces of the third substrate 512, which are electrically connected toeach other. A method of forming the terminals 580 and 581 is not limitedto the above-mentioned structure.

The terminal 580 formed on the third substrate 512 is electricallyconnected through the third bonding layer 513 to the terminal 570 thatis formed simultaneously with the first electrodes 550 and 560.

In this manner, a flexible light-emitting device interposed between theplastic substrates 510 and 512 can be obtained. With the use of the samematerial for the second substrate 510 and the third substrate 512, thesubstrates 510 and 512 have the same thermal expansion coefficient. As aresult, the substrates 510 and 512 can be hardly affected by a stressstrain due to change in temperature.

As shown in FIG. 12C, the terminal 581 formed so as not to be in contactwith the third bonding layer 513 but to be in contact with the thirdsubstrate 512 and the terminal 591 included in an FPC 590 are connectedto each other through a fourth bonding layer 592 made of an electricallyconductive resin having anisotropy.

Next, shown in FIG. 12C, the OLED panel is sealed by the a plastic film521 in which he sealing film 520 is deposited. When the sealing isexecuted, the sealing film 520 is arranged between the plastic film 521and the OLED (not shown in the figure).

In this embodiment, as a sealing film 520, an inorganic insulating film520 a, an organic insulating film 520 b and inorganic insulating film520 c are formed from the side of the plastic film 521.

The light-emitting device manufactured according to this embodimentallows the manufacture of an element employing a semiconductor (forexample, a TFT) without being limited by a heat resistance of theplastic substrate. Thus, the light-emitting device having extremely highperformance can be obtained.

Although the first bonding layer 502 is made of SOG and is removed withhydrogen fluoride in this embodiment, the present invention is notlimited to this structure. A material and a removal method of the firstbonding layer 502 can be suitably determined by those who carry out theinvention. It is important to determine a material and a removal methodof the first bonding layer 502 so that the substrates, the element andthe films other than the first bonding layer 502, which are not desiredto be removed, are not removed with removal of the first bonding layer502 and does not affect the operation of the light-emitting device.Moreover, it is also important that a material of the first bondinglayer 502 does not allow its removal in the process other than theremoval step of the first bonding layer 502.

For example, an organic material, which is entirely or partiallyvaporized by radiation of a laser beam, can be used as the first bondinglayer 502. Additionally, it is desirable that a material having laserbeam absorbance, for example, a colored or black material (for example,a resin material containing a black colorant) is used so that a laserbeam is efficiently absorbed only by the first bonding layer 502 in thecase where a second harmonic wave from a YAG laser is used. The firstbonding layer 502, which is not vaporized in a heat treatment in theelement formation steps, is used.

Each of the first, second and third bonding layers may be eithersingle-layered or multi-layered. An amorphous silicon film or a DLC filmmay be provided between the bonding layer and the substrate.

The first bonding layer 502 may be formed of an amorphous silicon film,and in the later step, the first substrate may be peeled off byradiation of a laser beam onto the first bonding layer 502. In thiscase, in order to facilitate the peeling of the first substrate, it ispreferred to use an amorphous silicon film containing a large amount ofhydrogen. Hydrogen contained in the amorphous silicon film is vaporizedby radiation of a laser beam, so that the first substrate can be easilypeeled off.

As a laser beam, a pulse or a continuous wave excimer laser, a YAG laseror a YVO₄ laser can be used. A laser beam is radiated onto the firstbonding layer through the first substrate so as to vaporize only thefirst bonding layer to peel off the first substrate. Therefore, as thefirst substrate, it is preferred to use a substrate having a thicknesslarger than that of the second and third substrates, which allows atleast a radiated laser beam to pass through, typically a substratehaving light transmittance, for example, a glass substrate, a quartzsubstrate or the like.

In the present invention, in order to allow a laser beam to pass throughthe first substrates it is necessary to suitably select the type of alaser beam and the first substrate. For example, when a quartz substrateis used as the first substrate, a YAG laser (fundamental wave (1064 nm),a second harmonic wave (532 nm), a third harmonic wave (355 nm), and afourth harmonic wave (266 nm)) or an excimer laser (wavelength: 308 nm)is used to form a linear beam which is in turn allowed to pass throughthe quartz substrate. It is noticed that an excimer laser beam does notpass through a glass substrate. Therefore, when a glass substrate isused as the first substrate, a fundamental wave, a second harmonic waveor a third harmonic wave of the YAG laser, preferably, a second harmonicwave (wavelength: 532 nm), is used to form a linear beam which is inturn allowed to pass through the glass substrate.

Alternatively, a method of separating the first substrate by spraying afluid (a pressure-applied liquid or gas) on the first bonding layer(typically, a water jet method) or a combination with this method can beused.

In the case where the first bonding layer is made of an amorphoussilicon film, the first bonding layer may be removed by using hydrazine.

Alternatively, a method of separating the first substrate by etching,described in a U.S. Pat. No. 5,821,138 may be used. Specifically, anapplied silicon oxide film (SOG) may be used as the first bonding layerwhich is removed by hydrogen fluoride. In this case, it is importantthat the silicon oxide film, which is not desired to be removed, isformed to have a fine structure through a sputtering or a CVD method sothat the silicon oxide film provides a high selection ratio when thefirst bonding layer is to be removed with hydrogen fluoride.

With such a structure, even if substrates having an extremely smallthickness, specifically, 50 to 300 μm, preferably 150 to 200 μm are usedas the second and third substrates, a light-emitting device with highreliability can be obtained. It was difficult to form an element on sucha thin substrate by using a conventionally known manufacturingapparatus. However, since the element is formed with being bonded ontothe first substrate, a manufacturing apparatus can be used with the useof a thick substrate without any alteration of the apparatus.

With the use of the sealing film including the multi-layered insulatingfilm, it is possible to effectively restrain the degradation due topenetration of moisture or oxygen. Moreover, a crack is prevented fromoccurring upon bend of the substrate. As a result, a light-emittingdevice having enhanced flexibility can be realized.

This embodiment can be implemented by—combining freely with Embodiment 1or 2.

Embodiment 7

In this embodiment, a method of forming TFT of a driving circuit (asource signal line driver circuit and a gate signal line driver circuit)arranged in the periphery of the pixel portion and a pixel portion willbe explained in detail. In this embodiment, in relation to the drivercircuit, CMOS circuit is only shown as a basic unit for briefdescription.

First, as shown in FIG. 13A, a first bonding film 5001 formed ofamorphous silicon film is formed and having a thickness of from 100 to500 nm (preferably 300 nm) on a first substrate 5000 formed of glasssuch as barium borosilicate glass or alumino borosilicate glassrepresented by #7059 glass and #1737 glass of CORNING Corporation, etc.The first bonding film 5001 is formed by using a low pressure thermalCVD method, plasma CVD method, sputtering method or evaporation methodcan be used. The first bonding film 5001 is formed by using sputteringmethod in this embodiment.

Next, a base film 5002 formed of an insulating film such as a siliconoxide film, a silicon oxynitride film or a silicon nitride oxide film isformed on the first bonding film 5001. The base film 5002 has an effectof protecting an element formed on a substrate 5000 when the firstbonding layer 5001 is removed to peel off the substrate 5000. Forexample, a silicon nitride oxide film formed from SiH₄, NH₃ and N₂O bythe plasma CVD method and having a thickness of from 10 to 200 nm(preferably 50 to 100 nm) is formed. Similarly, a hydrogenerated siliconnitride oxide film formed from SiH₄ and N₂O and having a thickness offrom 50 to 200 nm (preferably 100 to 150 nm) is layered thereon. In thisembodiment, the base film 5002 has a two-layer structure, but may alsobe formed as a single layer film of one of the above insulating films,or a laminate film having more than two layers of the above insulatingfilms.

Island-like semiconductor layers 5003 to 5006 are formed from acrystalline semiconductor film obtained by conducting lasercrystallization or a known thermal crystallization on a semiconductorfilm having an amorphous structure. These island-like semiconductorlayers 5003 to 5006 each has a thickness of from 25 to 80 nm (preferably30 to 60 nm). No limitation is put on the material of the crystallinesemiconductor film, but the crystalline semiconductor film is preferablyformed from silicon, a silicon germanium (SiGe) alloy, etc.

When the crystalline semiconductor film is to be manufactured by thelaser crystallization method, an excimer laser, a YAG laser and an YVO₄laser of a pulse oscillation type or continuous light emitting type areused. When these lasers are used, it is preferable to use a method inwhich a laser beam radiated from a laser emitting device is convergedinto a linear shape by an optical system and then is irradiated to thesemiconductor film. A crystallization condition is suitably selected byan operator. When the excimer laser is used, pulse oscillation frequencyis set to 300 Hz, and laser energy density is set to from 100 to 400mJ/cm² (typically 200 to 300 mJ/cm². When the YAG laser is used, pulseoscillation frequency is preferably set to from 30 to 300 kHz by usingits second harmonic, and laser energy density is preferably set to from300 to 600 mJ/cm² (typically 350 to 500 mJ/cm²). The laser beamconverged into a linear shape and having a width of from 100 to 1000 μm,e.g. 400 μm is, is irradiated to the entire substrate face. At thistime, overlapping ratio of the linear laser beam is set to from 50 to90%.

Next, a gate insulating film 5007 covering the island-like semiconductorlayers 5003 to 5006 is formed. The gate insulating film 5007 is formedfrom an insulating film containing silicon and having a thickness offrom 40 to 150 nm by using the plasma CVD method or a sputtering method.In this embodiment, the gate insulating film 5007 is formed from asilicon nitride oxide film of 120 nm in thickness. However, the gateinsulating film is not limited to such a silicon nitride oxide film, butit may be an insulating film containing other and having a single layeror a laminated layer structure. For example, when a silicon oxide filmis used, TEOS (Tetraethyl Orthosilicate) and O₂ are mixed by the plasmaCVD method, the reaction pressure is set to 40 Pa, the substratetemperature is set to from 300 to 400° C., and the high frequency (13.56MHz) power density is set to from 0.5 to 0.8 W/cm² for electricdischarge. Thus, the silicon oxide film can be formed by discharge. Thesilicon oxide film manufactured in this way can then obtain preferablecharacteristics as the gate insulating film by thermal annealing at from400 to 500° C.

A first conductive film 5008 and a second conductive film 5009 forforming a gate electrode are formed on the gate insulating film 5007. Inthis embodiment, the first conductive film 5008 having a thickness offrom 50 to 100 nm is formed from Ta, and the second conductive film 5009having a thickness of from 100 to 300 nm is formed from W.

The Ta film is formed by a sputtering method, and the target of Ta issputtered by Ar. In this case, when suitable amounts of Xe and Kr areadded to Ar, internal stress of the Ta film is released, and pealing offthis film can be prevented. Resistivity of the Ta film of α phase isabout 20 μΩcm, and this Ta film can be used for the gate electrode.However, resistivity of the Ta film of β phase is about 180 μΩcm, and isnot suitable for the gate electrode. When tantalum nitride having acrystal structure close to that of the a phase of Ta and having athickness of about 10 to 50 nm is formed in advance as the base for theTa film to form the Ta film of the a phase, the Ta film of a phase canbe easily obtained.

The W film is formed by the sputtering method with W as a target.Further, the W film can be also formed by a thermal CVD method usingtungsten hexafluoride (WF₆). In any case, it is necessary to reduceresistance to use this film as the gate electrode. It is desirable toset resistivity of the W film to be equal to or smaller than 20 μΩcm.When crystal grains of the W film are increased in size, resistivity ofthe W film can be reduced. However, when there are many impurityelements such as oxygen, etc. within the W film, crystallization isprevented and resistivity is increased. Accordingly, in the case of thesputtering method, a W-target of 99.9999% or 99.99% in purity is used,and the W film is formed by taking a sufficient care of not mixingimpurities from a gaseous phase into the W film time when the film is tobe formed. Thus, a resistivity of from 9 to 20 μΩcm can be realized.

In this embodiment, the first conductive film 5008 is formed from Ta,and the second conductive film 5009 is formed from W. However, thepresent invention is not limited to this case. Each of these conductivefilms may also be formed from an element selected from Ta, W, Ti, Mo, Aland Cu, or an alloy material or a compound material having theseelements as principal components. Further, a semiconductor filmrepresented by a poly crystal silicon film doped with an impurityelement such as phosphorus may also be used. Examples of combinationsother than those shown in this embodiment include: a combination inwhich the first conductive film 5008 is formed from tantalum nitride(TaN), and the second conductive film 5009 is formed from W; acombination in which the first conductive film 5008 is formed fromtantalum nitride (TaN), and the second conductive film 5009 is formedfrom Al; and a combination in which the first conductive film 5008 isformed from tantalum nitride (TaN), and the second conductive film 5009is formed from Cu.

Next, a mask 5010 is formed from a resist, and first etching processingfor forming an electrode and wiring is performed. In this embodiment, anICP (Inductively Coupled Plasma) etching method is used, and CF₄ and Cl₂are mixed with a gas for etching. RF (13.56 MHz) power of 500 W isapplied to the electrode of coil type at a pressure of 1 Pa so thatplasma is generated. RF (13.56 MHz) of 100 W power is also applied to asubstrate side (sample stage), and a substantially negative self biasvoltage is applied. When CF₄ and Cl₂ are mixed, the W film and the Tafilm are etched to the same extent.

Under the above etching condition, end portions of a first conductivelayer and a second conductive layer are formed into a tapered shape byeffects of the bias voltage applied to the substrate side by making theshape of the mask formed from the resist into an appropriate shape. Theangle of a taper portion is set to from 15° to 45°. It is preferable toincrease an etching time by a ratio of about 10 to 20% so as to performthe etching without leaving the residue on the gate insulating film.Since a selection ratio of a silicon nitride oxide film to the W filmranges from 2 to 4 (typically 3), an exposed face of the silicon nitrideoxide film is etched by about 20 to 50 nm by over-etching processing.Thus, conductive layers 5011 to 5016 of a first shape (first conductivelayers 5011 a to 5016 a and second conductive layers 5011 b to 5016 b)formed of the first and second conductive layers are formed by the firstetching processing. A region that is not covered with the conductivelayers 5011 to 5016 of the first shape is etched by about 20 to 50 nm inthe gate insulating film 5007, so that a thinned region is formed. (SeeFIG. 13A).

Then, an impurity element for giving an n-type conductivity is added byperforming first doping processing. A doping method may be either an iondoping method or an ion implantation method. The ion doping method iscarried out under the condition that a dose is set to from 1×10¹³ to5×10¹⁴ atoms/cm², and an acceleration voltage is set to from 60 to 100keV. An element belonging to group 15, typically, phosphorus (P) orarsenic (As) is used as the impurity element for giving the n-typeconductivity. However, phosphorus (P) is used here. In this case, theconductive layers 5011 to 5015 serve as masks with respect to theimpurity element for giving the n-type conductivity, and first impurityregions 5017 to 5025 are formed in a self-aligning manner. The impurityelement for giving the n-type conductivity is added to the firstimpurity regions 5017 to 5025 in a concentration range from 1×10²⁰ to1×10²¹ atoms/cm³. (See FIG. 13B).

Second etching processing is next performed without removing the resistmask as shown in FIG. 13C. A W film is etched selectively by using CF₄,Cl₂ and O₂. The conductive layers 5026 to 5031 of a second shape (firstconductive layers 5026 a to 5031 a and second conductive layers 5026 bto 5031 b) are formed by the second etching processing. A region of thegate insulating film 5007, which is not covered with the conductivelayers 5026 to 5031 of the second shape, is further etched by about 20to 50 nm so that a thinned region is formed.

An etching reaction in the etching of the W film using the mixed gas ofCF₄ and Cl₂ and the Ta film can be assumed from the vapor pressure of aradical or ion species generated and a reaction product. When the vaporpressures of a fluoride and a chloride of W and Ta are compared, thevapor pressure of WF₆ as a fluoride of W is extremely high, and vaporpressures of other WCl₅, TaF₅ and TaCl₅ are approximately equal to eachother. Accordingly, both the W film and the Ta film are etched using themixed gas of CF₄ and Cl₂. However, when a suitable amount of O₂ is addedto this mixed gas. CF₄ and O₂ react and become CO and F so that a largeamount of F-radicals or F-ions is generated. As a result, the etchingspeed of the W film whose fluoride has a high vapor pressure isincreased. In contrast to this, the increase in etching speed isrelatively small for the Ta film when F is increased. Since Ta is easilyoxidized in comparison with W, the surface of the Ta film is oxidized byadding O₂. Since no oxide of Ta reacts with fluorine or chloride, theetching speed of the Ta film is further reduced. Accordingly, it ispossible to make a difference in etching speed between the W film andthe Ta film so that the etching speed of the W film can be set to behigher than that of the Ta film.

As shown in FIG. 14A, second doping processing is then performed. Inthis case, an impurity element for giving the n-type conductivity isdoped in a smaller dose than in the first doping processing and at ahigh acceleration voltage by reducing a dose lower than that in thefirst doping processing. For example, the acceleration voltage is set tofrom 70 to 120 keV, and the dose is set to 1×10¹³ atoms/cm². Thus, a newimpurity region is formed inside the first impurity region formed in theisland-like semiconductor layer in FIG. 13B. In the doping, theconductive layers 5026 to 5030 of the second shape are used as maskswith respect to the impurity element, and the doping is performed suchthat the impurity element is also added to regions underside the firstconductive layers 5026 a to 5030 a. Thus, third impurity regions 5032 to5041 are formed. The third impurity regions 5032 to 5036 containphosphorus (P) with a gentle concentration gradient that conforms withthe thickness gradient in the tapered portions of the first conductivelayers 5026 a to 5030 a. In the semiconductor layers that overlap thetapered portions of the first conductive layers 5026 a to 5030 a theimpurity concentration is slightly lower around the center than at theedges of the tapered portions of the first conductive layers 5026 a to5030 a. However, the difference is very slight and almost the sameimpurity concentration is kept throughout the semiconductor layers.

Third etching treatment is then carried out as shown in FIG. 14B. CHF,is used as etching gas, and reactive ion etching (RIE) is employed.Through the third etching treatment, the tapered portions of the firstconductive layers 5026 a to 5031 a are partially etched to reduce theregions where the first conductive layers overlap the semiconductorlayers. Thus formed are third shape conductive layers 5037 to 5042(first conductive layers 5037 a to 5042 a and second conductive layers5037 b to 5042 b). At this point, regions of the gate insulating film5007 that are not covered with the third shape conductive layers 5037 to5042 are further etched and thinned by about 20 to 50 nm.

Third impurity regions 5032 to 5036 are formed through the third etchingtreatment. The third impurity regions 5032 a to 5036 a that overlap thefirst conductive layers 5037 a to 5041 a, respectively, and secondimpurity regions 5032 b to 5036 b each formed between a first impurityregion and a third impurity region.

As shown in FIG. 14C, fourth impurity regions 5043 to 5054 having theopposite conductivity type to the first conductivity type are formed inthe island-like semiconductor layers 5004 and 5006 for forming p-channelTFTs. The third shape conductive layers 5038 b and 5041 b are used asmasks against the impurity element and impurity regions are formed in aself-aligning manner. At this point, the island-like semiconductorlayers 5003 and 5005 for forming n-channel TFTs and the wiring portion5042 are entirely covered with a resist mask 5200. The impurity regions5043 to 5054 have already been doped with phosphorus in differentconcentrations. The impurity regions 5043 to 5054 are doped withdiborane (B₂H₆) through ion doping such that diborane dominatesphosphorus in each region and each region contain the impurity elementin a concentration of 2×10²⁰ to 2×10²¹ atoms/cm⁻³.

Through the steps above, the impurity regions are formed in therespective island-like semiconductor layers. The third shape conductivelayers 5037 to 5041 overlapping the island-like semiconductor layersfunction as gate electrodes. Reference numeral 5042 function asisland-like source signal line.

After resist mask 5200 is removed, a step of activating the impurityelements added to the island-like semiconductor layers is performed tocontrol the conductivity type. This process is performed by a thermalannealing method using a furnace for furnace annealing. Further, a laserannealing method or a rapid thermal annealing method (RTA method) can beapplied. In the thermal annealing method, this process is performed at atemperature of from 400 to 700° C., typically from 500 to 600° C. withina nitrogen atmosphere in which oxygen concentration is equal to orsmaller than 1 ppm and is preferably equal to or smaller than 0.1 ppm.In this embodiment, heat treatment is performed for four hours at atemperature of 500° C. When a wiring material used in the third shapeconductive layers 5037 to 5042 is weak against heat, it is preferable toperform activation after an interlayer insulating film (having siliconas a principal component) is formed in order to protect wiring, etc.

Further, the heat treatment is performed for 1 to 12 hours at atemperature of from 300 to 450° C. within an atmosphere including 3 to100% of hydrogen so that the island-like semiconductor layer ishydrogenerated. This step is to terminate a dangling bond of thesemiconductor layer by hydrogen thermally excited. Plasma hydrogenation(using hydrogen excited by plasma) may also be performed as anothermeasure for hydrogenation.

Next, as shown in FIG. 15A, a first interlayer insulating film 5055 isformed from a nitride oxide silicon film to 100 to 200 nm thick. Thesecond interlayer insulating film 5056 from an organic insulatingmaterial is formed on the first interlayer insulating film. Thereafter,contact holes are formed through the first interlayer insulating film5055, the second interlayer insulating film 5056 and the gate insulatingfilm 5007. Each wiring (including a connecting wiring and a signal line)5057 to 5062, and 5064 are patterned and formed. Thereafter, a pixelelectrode 5063 coming in contact with the connecting wiring 5062 ispatterned and formed.

A film having an organic resin as a material is used as the secondinterlayer insulating film 5056. Polyimide, polyamide, acrylic, BCB(benzocyclobutene), etc. an be used as this organic resin. Inparticular, since the second interlayer insulating film 5056 is providedmainly for planarization, acrylic excellent in leveling the film ispreferable. In this embodiment, an acrylic film having a thickness thatcan sufficiently level a level difference caused by the TFT is formed.The film thickness thereof is preferably set to from 1 to 5 μm (isfurther preferably set to from 2 to 4 μm).

In the formation of the contact holes, contact holes reaching n-typeimpurity regions 5017, 5018, 5021 and 5023 or p-type impurity regions5043 to 5054, a contact hole reaching wiring 5042, an contact holereaching an electric current supply line (not illustrated), and contactholes reaching gate electrodes (not illustrated) are formed.

Further, a laminate film of a three-layer structure is patterned in adesired shape and is used as wiring (including a connecting wiring andsignal line) 5057 to 5062 and 5064. In this three-layer structure, a Tifilm of 100 [nm] in thickness, an aluminum film containing Ti of 300[nm] in thickness, and a Ti film of 150 [nm] in thickness arecontinuously formed by the sputtering method. However, anotherconductive film may also be used.

In this embodiment, an ITO film of 110 nm in thickness is formed as apixel electrode 5063, and is patterned. Contact is made by arranging thepixel electrode 5063 such that this pixel electrode 5063 comes incontact with the connecting electrode 5062 and is overlapped with thisconnecting wiring 5062. Further, a transparent conductive film providedby mixing 2 to 20% of zinc oxide (ZnO) with indium oxide may also beused. This pixel electrode 5063 becomes an anode of the OLED. (See FIG.15A)

As shown in FIG. 15B, an insulating film (a silicon oxide film in thisembodiment) containing silicon and having a thickness of 500 nm is nextformed. A third interlayer insulating film 5065 is formed in which anopening is formed in a position corresponding to the pixel electrode5063. When the opening is formed, a side wall of the opening can easilybe tapered by using the wet etching method. When the side wall of theopening is not gentle enough, deterioration of an organic light emittinglayer caused by a level difference becomes a notable problem.

Next, an organic light emitting layer 5066 and a cathode (MgAgelectrode) 5067 are continuously formed by using the vacuum evaporationmethod without exposing to the atmosphere. The organic light emittinglayer 5066 has a thickness of from 80 to 200 nm (typically from 100 to120 nm), and the cathode 5067 has a thickness of from 180 to 300 nm(typically from 200 to 250 nm).

In this process, the organic light emitting layer is sequentially formedwith respect to a pixel corresponding to red, a pixel corresponding togreen and a pixel corresponding to blue. In this case, since the organiclight emitting layer has an insufficient resistance against a solution,the organic light emitting layer must be formed separately for eachcolor instead of using a photolithography technique. Therefore, it ispreferable to cover a portion except for desired pixels using a metalmask so that the organic light emitting layer is formed selectively onlyin a required portion.

Namely, a mask for covering all portions except for the pixelcorresponding to red is first set, and the organic light emitting layerfor emitting red light are selectively formed by using this mask. Next,a mask for covering all portions except for the pixel corresponding togreen is set, and the organic light emitting layer for emitting greenlight are selectively formed by using this mask. Next, a mask forcovering all portions except for the pixel corresponding to blue issimilarly set, and the organic light emitting layer for emitting bluelight are selectively formed by using this mask. Here, different masksare used, but instead the same single mask may be used repeatedly.

Here, a system for forming three kinds of OLED corresponding to RGB isused. However, a system in which an OLED for emitting white light and acolor filter are combined, a system in which the OLED for emitting blueor blue green light is combined with a fluorescent substance (afluorescent color converting medium: CCM), a system for overlapping theOLED respectively corresponding to R, G, and B with the cathodes(opposite electrodes) by utilizing a transparent electrode, etc. may beused.

A known material can be used as the organic light emitting layer 5066.An organic material is preferably used as the known material inconsideration of a driving voltage. For example, a four-layer structureconsisting of a hole injection layer, a hole transportation layer, alight emitting layer and an electron injection layer is preferably usedfor the organic light emitting layer.

The cathode 5067 is formed next on the pixel (pixel on the same line)included the switching TFT in which the gate electrode is connected tothe same gate signal line by using a metal mask. This embodiment usesMgAg for the cathode 5067 but it is not limited thereto. Other knownmaterials may be used for the cathode 5067.

Finally, a planarization film 5068 formed of resin and having athickness of 300 nm is formed. In reality, the planarization film 5068plays a role of protecting the organic light emitting layer 5066 frommoisture, etc. However, reliability of OLED can be further improved byforming the planarization film 5068.

Thus, the state as shown in FIG. 15B is completed. Though not shown infigures, according to manufacturing method in Embodiment 3, the secondsubstrate providing sealing film is bonded to the planarization film5068 by using a second bonding layer. In addition, following steps canbe executed in according to methods shown in Embodiment Mode 1. Inaccordance of manufacturing method in Embodiment 4, the second substrateproviding sealing film is bonded to the planarization film 5068 by usinga second bonding layer. In addition, following steps can be executed inaccording to methods shown in Embodiment Mode 2.

In the process of forming the light-emitting device in this embodiment,the source signal line is formed from Ta and W that are materials of thegate electrodes, and the gate signal line is formed from Al that is awiring material of the source and drain electrodes for conveniences ofthe circuit construction and procedures in the process. Howeverdifferent materials may also be used.

The light-emitting device in this embodiment has very high reliabilityand improved operating characteristics by arranging the TFTs of theoptimal structures in a driving circuit portion in addition to the pixelportion. Further, in a crystallization process, crystallinity can bealso improved by adding a metal catalyst such as Ni. Thus, a drivingfrequency of the source signal line driving circuit can be set to 10 MHzor more.

First, the TFT having a structure for reducing hot carrier injection soas not to reduce an operating speed as much as possible is used as ann-channel type TFT of a CMOS circuit forming the driving circuitportion. Here, the driving circuit includes a shift register, a buffer,a level shifter, a latch in line sequential driving, a transmission gatein dot sequential driving, etc.

In the case of this embodiment, an active layer of the n-channel typeTFT includes a source region, a drain region, an overlap LDD region (Lovregion) that is overlapped with the gate electrode through the gateinsulating film, an offset LDD region (Loff region) that is notoverlapped with the gate electrode through the gate insulating film, andchannel formation region.

Deterioration by the hot carrier injection in the p-channel type TFT ofthe CMOS circuit is almost negligible. Therefore, it is not necessary toparticularly form the LDD region in this n-channel type TFT. However,similar to the n-channel type TFT, the LDD region can be formed as a hotcarrier countermeasure.

Further, when the CMOS circuit for bi-directionally flowing an electriccurrent through a channel forming region, i.e., the CMOS circuit inwhich roles of the source and drain regions are exchanged is used in thedriving circuit, it is preferable for the n-channel type TFT thatconstitutes the CMOS circuit to form LDD regions such that the channelforming region is sandwiched between the LDD regions. As an example ofthis, a transmission gate used in the dot sequential driving is given.When a CMOS circuit required to reduce an OFF-state current value asmuch as possible is used in the driving circuit, the n-channel type TFTforming the CMOS circuit preferably has a Lov region. The transmissiongate used in the dot sequential driving can be given also as an exampleas such.

Furthermore, in accordance with the processes shown in this embodiment,the number of photomasks can be reduced that is need for manufacturingthe light-emitting device. As a result, the processes can be reduced,and this contributes to a reduction in the manufacturing costs and anincrease in throughput.

Note that it is possible to implement Embodiment 7 in combination withEmbodiments 1 to 5.

Embodiment 8

In Embodiment 8, a structure of a light-emitting device usinginverse-stagger type TFTs according to the present invention will bedescribed.

FIG. 16 is a cross-sectional view showing a light-emitting deviceaccording to the present invention. A sealing film 601 is formed on aflexible second substrate 602 and a third substrate 672. The sealingfilm 601 includes an inorganic insulating film 601 a, a organicinsulating film 601 b and an inorganic insulating film 601 c.

Between the flexible second substrate 602 and the third substrate 672.TFTs, an OLED and other elements are formed. In this embodiment, a TFT604 a included in a driving circuit 610 and TFTs 604 b and 604 cincluded in a pixel portion 611 are shown as representative examples.

An OLED 605 includes a pixel electrode 640, an organic light emittinglayer 641 and a cathode 642.

The TFT 604 a includes gate electrodes 613 and 614, an insulating film612 formed so as to be in contact with the gate electrodes 613 and 614,and a semiconductor film 615 formed so as to be in contact with theinsulating film 612. The TFT 604 b includes gate electrodes 620 and 621,the insulating film 612 formed so as to be in contact with the gateelectrodes 620 and 621, and a semiconductor film 622 formed so as to bein contact with the insulating film 612. The TFT 604 c includes a gateelectrode 630, the insulating film 612 formed so as to be in contactwith the gate electrode 630, and a semiconductor film 631 formed so asto be in contact with the insulating film 612.

Although there is shown the example where the inverse-stagger type TFTsare used in the light-emitting device manufactured according toEmbodiment 3, the structure of this embodiment is not limited thereto.The inverse-stagger type TFTs may be used in the light-emitting devicemanufactured according to Embodiment 4.

Embodiment 8 can be carried out in free combination with Embodiments 1to 5.

Embodiment 9

In Embodiment 9, an example where a bonding layer is removed by sprayinga fluid thereon will be described.

As a method of spraying a fluid, a method of spraying a high-pressurewater flow from a nozzle on an object (referred to as a water jetmethod) or a method of spraying a high-pressure gas flow on an objectcan be used. In the case of the water jet method, an organic solvent, anacid solution or an alkaline solution may be used instead of water. As agas flow, air, a nitrogen gas, a carbon dioxide gas or a rare gas may beused. Furthermore, a plasma obtained from these gases may also be used.It is important to select an appropriate fluid in accordance with amaterial of the bonding layer and materials of the films and substrateswhich are not desired to be removed so that such films and substratesare not removed with removal of the bonding layer.

As a bonding layer, a porous silicon layer or a silicon layer to whichhydrogen, oxygen, nitrogen or a rare gas is added is used. In the casewhere a porous silicon layer is used, an amorphous silicon film or apolycrystalline silicon film may be subjected to anodization to provideporousness thereto for use.

FIG. 17 shows removal of a bonding layer by a water jet method. An OLED1604 is provided between substrates 1601 and 1602. The OLED 1604 iscovered with an insulating film 1603.

An insulating film 1605 and a bonding layer 1606 are provided betweenthe substrate 1601 and the OLED 1604. The bonding layer 1606 is incontact with the substrate 1601. Although only the OLED isrepresentatively shown in FIG. 17. TFTs and other elements are normallyprovided between the insulating films 1605 and 1603.

The bonding layer 1606 may have a thickness of 0.1 to 900 μm(preferably, 0.5 to 10 μm). In Embodiment 9, an SOG film having athickness of 1 μm is used as the bonding layer 1606.

A fluid 1607 is sprayed from a nozzle 1608 onto the bonding layer 1606.In order to efficiently spray the fluid 1607 onto the entire exposedportion of the bonding layer 1606, it is recommended to spray the fluidwhile rotating the bonding layer 1606 around a central lineperpendicular to the substrate 1601, as is indicated with an arrow inFIG. 17.

The fluid 1607, to which a pressure of 1×10⁷ to 1×10⁹ Pa (preferably,3×10⁷ to 5×10⁸ Pa) is applied, is sprayed from the nozzle 1608 onto theexposed portion of the bonding layer 1606. Since the sample rotates, thefluid 1607 is sprayed along the exposed surface of the bonding layer1606.

When the fluid emitted from the nozzle 1608 is sprayed onto the bondinglayer 1606, the bonding layer is broken due to impact for its fragilityand then is removed or is chemically removed. As a result, the bondinglayer 1606 is broken or removed to separate the substrate 1601 and theinsulating film 1605 from each other. In the case where the separationis achieved by breaking the bonding layer 1606, the remaining bondinglayer may be removed by etching.

As the fluid 1607, a liquid such as water, an organic solvent, an acidsolution or an alkaline solution may be used. Alternatively, air, anitrogen gas, a carbon dioxide gas or a rare gas may be also used.Furthermore, a plasma obtained from these gases may be used.

Embodiment 9 can be carried out in combination with Embodiments 1 to 8.

Embodiment 10

In this embodiment, an external light emitting quantum efficiency can beremarkably improved by using an organic light emitting material by whichphosphorescence from a triplet exciton can be employed for emitting alight. As a result, the power consumption of OLED can be reduced, thelifetime of OLED can be elongated and the weight of OLED can belightened.

The following is a report where the external light emitting quantumefficiency is improved by using the triplet exciton (T. Tsutsui, C.Adachi, S. Saito, Photochemical processes in Organized MolecularSystems, ed. K. Honda, (Elsevier Sci. Pub., Tokyo, 1991) p. 437).

The molecular formula of an organic light emitting material (coumarinpigment) reported by the above article is represented as follows.

(M. A. Baldo, D. F. O' Brien, Y. You, A. Shoustikov, S. Sibley, M. E.Thompson, S. R. Forrest, Nature 395 (1998) p. 151)

The molecular formula of an organic light emitting material (Pt complex)reported by the above article is represented as follows.

(M. A. Baldo, S. Lamansky, P. E. Burrows, M. E. Thompson. S. R. Forrest,Appl. Phys. Lett., 75 (1999) p. 4.)(T. Tsutsui, M.-J. Yang, M. Yahiro, K. Nakamura. T. Watanabe, T. Tsuji.Y. Fukuda, T. Wakimoto, S. Mayaguchi, Jpn, Appl. Phys., 38 (12B) (1999)L1502)

The molecular formula of an organic light emitting material (Ir complex)reported by the above article is represented as follows.

As described above, if phosphorescence from a triplet exciton can be putto practical use, it can realize the external light emitting quantumefficiency three to four times as high as that in the case of usingfluorescence from a singlet exciton in principle.

The structure according to this embodiment can be freely implemented incombination of any structures of the Embodiments 1 to 9.

Embodiment 11

A film made of an organic light emitting material is generally formed byan ink jet method, a spin-coating method or an evaporation method. InEmbodiment 11, a method for forming an organic light emitting layerother than the above-mentioned methods will be described.

In this embodiment, a film containing molecular assemblies of an organiclight emitting material is formed on a substrate under an inert gasatmosphere by spraying, using a colloidal solution in which molecularassemblies constituting the organic light emitting material aredispersed (also referred to as a sol). The organic light emittingmaterial is present as particles, each being an assembly of severalmolecules in a liquid.

FIG. 18 shows the formation of an organic light emitting layer 650 byspraying a composition from a nozzle (not shown) in an inert gas (inthis embodiment, a nitrogen gas). The composition is obtained bydispersing tris (2-phenylpyridine) iridium (Ir(ppy)₃) which is aniridium complex serving as an organic light emitting material, andbathocupuroine (BCP) which is an organic light emitting material servingas a host (hereinafter, referred to as a host material) in toluene.

In FIG. 18, the organic light emitting layer 650 is selectively formedto have a thickness of 25 to 40 nm by using a mask 651. Both the iridiumcomplex and BCP are insoluble to toluene.

In practice, there are some cases where the organic light emitting layeris used in a single-layered form and the other cases where it is used ina multi-layered form. In the case where the organic light emitting layerhas a multi-layered structure, another (other) organic light emittinglayer(s) is (are) formed in a similar manner after formation of theorganic light emitting layer 650. In this case, all the depositedorganic light emitting layers are collectively referred to as theorganic light emitting layer.

A film formation method of this embodiment allows the formation of afilm even if the organic light emitting material in a liquid is in anystate. Particularly, this method permits an organic light emitting layerwith good quality to be formed by using an organic light emittingmaterial that is hardly dissolved. Moreover, since a film is formed byspraying a liquid containing an organic light emitting material with useof a carrier gas, the film formation can be achieved within a shortperiod of time. A method of producing a liquid containing an organiclight emitting material to be sprayed can be extremely simplified.Furthermore in this embodiment, a mask is used to form a film having adesired pattern, so that the film formation is conducted through anopening of the mask. In addition, in order to efficiently use anexpensive organic light emitting material, it is possible to collect theorganic light emitting material adhered to the mask for reuse.

The ink jet method and the spin-coating method have a restriction inthat an organic light emitting material having a high solubility to asolvent cannot be used. The evaporation has a restriction in that anorganic light emitting material which decomposes before evaporationcannot be used. However, the film formation method of this embodiment isnot affected by the above-mentioned restrictions.

As examples of the organic light emitting material suitable for the filmformation method of this embodiment, quinacridon, tris(2-phenylpyridine) iridium, bathocuproine, poly(1,4-phenylenevinylene),poly(1,4-naphthalenevinylene), poly(2-phenyl-1,4-phenylenevinylene),polythiophene, poly(3-phenylthiophene), poly (1,4-phenylene),poly(2,7-fluorene) and the like can be given.

The structure of Embodiment 11 can be carried out in free combinationwith any of Embodiments 1 to 10.

Embodiment 12

This embodiment gives descriptions that are more detailed of the pixelportion of the light-emitting device obtained by the present inventionin Embodiment 12. The top structure of the pixel portion is shown inFIG. 19A whereas the circuit diagram thereof is shown in FIG. 19B.Common reference symbols are used in FIG. 19A and FIG. 19B to becross-referred.

A switching TFT 802 has a source connected to a source wiring 815, adrain connected to a drain wiring 805 and gate electrodes 804 a and 804b which are derived from a gate wiring 803. The drain wiring 805 iselectrically connected to a gate electrode 807 of a current controllingTFT 806. The current controlling TFT 806 has a source electricallyconnected to a current supply line 816 and has a drain electricallyconnected to a drain wiring 817. The drain wiring 817 is electricallyconnected to a pixel electrode 818 indicated by the dotted line.Reference numeral 814 denotes an EL element.

A storage capacitor is formed here in a region denoted by 819. Thestorage capacitor 819 is composed of a semiconductor film 820 that iselectrically connected to the current supply line 816, an insulatingfilm (not shown) on the same layer as the gate insulating film, and thegate electrode 807. A capacitor composed of the gate electrode 807, thesame layer (not shown) as the first interlayer insulating film, and thecurrent supply line 816 may also be used as a storage capacitor.

This embodiment 12 can be combined with Embodiments 1 to 11.

Embodiment 13

This embodiment shows an example of the circuit structure of thelight-emitting device with reference to FIG. 20. The circuit structureshown in this embodiment is for digital driving. The structure accordingto this embodiment has a source side driver circuit 901, a pixel portion906 and a gate side driver circuit 907.

The source side driver circuit 901 is provided with a shift register902, a latch (A) 903, a latch (B) 904, and a buffer 905. In the case ofanalog driving, a sampling circuit (transfer gate) is provided in placeof the latches (A) and (B). The gate side driver circuit 907 is providedwith a shift register 908 and a buffer 909. However, the buffer 909 isnot always necessary to provide.

In this embodiment, the pixel portion 906 includes a plurality ofpixels, each of which is provided with OLED. It is preferable that acathode of OLED is electrically connected to a drain of a currentcontrolling TFT.

The source side driver circuit 901 and the gate side driver circuit 907are composed of n-channel TFTs or p-channel TFTs obtained in accordancewith Embodiments 2 to 4.

Though not shown, another gate side driver circuit may be added oppositethe gate side driver circuit 907 across the pixel portion 906. In thiscase, two of the gate side driver circuits have the same structure andshare a gate wiring, so that the other can send a gate signal in placeof the broken one to make the pixel portion operate normally.

This embodiment can be combined with Embodiments 1 to 12.

Embodiment 14

Being self-luminous, a light-emitting device using a light emittingelement has better visibility in bright places and wider viewing anglethan liquid crystal display devices. Therefore, the light-emittingdevice can be used to the display units of various electric appliances.

Given as examples of an electric appliance that employs a light-emittingdevice manufactured in accordance with the present invention are videocameras, digital cameras, goggle type displays (head mounted displays),navigation systems, audio reproducing devices (such as car audio andaudio components), lap-top computers, game machines, portableinformation terminals (such as mobile computers, cellular phones,portable game machines, and electronic books), and image reproducingdevices equipped with recording media (specifically, devices with adisplay device that can reproduce data in a recording medium such as adigital video disk (DVD) to display an image of the data). Wide viewingangle is important particularly for portable information terminalsbecause their screens are often slanted when they are looked at.Therefore, it is preferable for portable information terminals to employthe light-emitting device using the light emitting element. Specificexamples of these electric appliances are shown in FIGS. 21A to 21D.

FIG. 21A shows a digital still camera, which is composed of a main body2101, a display unit 2102, an image receiving unit 2103, operation keys2104, an external connection port 2105, a shutter 2106, etc. Thelight-emitting device manufactured in accordance with the presentinvention can be applied to the display unit 2102.

FIG. 21B shows a mobile computer, which is composed of a main body 2301,a display unit 2302, a switch 2303, operation keys 2304, an infraredport 2305, etc. The light-emitting device manufactured in accordancewith the present invention can be applied to the display unit 2302.

FIG. 21C shows a goggle type display (head mounted display), which iscomposed of a main body 2501, display units 2502, and arm units 2503.The light-emitting device manufactured in accordance with the presentinvention can be applied to the display units 2502.

FIG. 21D shows a portable telephone, which is composed of a main body2701, a case 2702, a display unit 2703, an audio input unit 2704, anaudio output unit 2705, operation keys 2706, an external connection port2707, an antenna 2708, etc. The light-emitting device manufactured inaccordance with the present invention can be applied to the display unit2703. If the display unit 2703 displays white letters on blackbackground, the cellular phone consumes less power.

If the luminance of light emitted from organic materials is raised infuture, the light-emitting device can be used in front or rearprojectors by enlarging outputted light that contains image informationthrough a lens or the like and projecting the light.

These electric appliances now display with increasing frequencyinformation sent through electronic communication lines such as theInternet and CATV (cable television), especially, animation information.Since organic materials have very fast response speed, thelight-emitting device is suitable for animation display.

In the light emitting device, light emitting portions consume power andtherefore it is preferable to display information in a manner thatrequires less light emitting portions. When using the light-emittingdevice in display units of portable information terminals, particularlycellular phones and audio reproducing devices that mainly display textinformation, it is preferable to drive the device such that non-lightemitting portions form a background and light emitting portions formtext information.

As described above, the application range of the light-emitting deviceof the present invention is so wide that it is applicable to electricappliances of any field. The electric appliances of this embodiment canemploy any light-emitting device shown in Embodiments 1 to 13.

Embodiment 15

Organic light emitting materials used in OLEDs are roughly divided intolow molecular weight materials and high molecular weight materials. Alight-emitting device of the present invention can employ a lowmolecular weight organic light emitting material and a high molecularweight organic light emitting material both.

A low molecular weight organic light emitting material is formed into afilm by evaporation. This makes it easy to form a laminate structure,and the efficiency is increased by layering films of different functionssuch as a hole transporting layer and an electron transporting layer.

Examples of low molecular weight organic light emitting material includean aluminum complex having quinolinol as a ligand (Alq₃) and atriphenylamine derivative (TPD).

On the other hand, a high molecular weight organic light emittingmaterial is physically stronger than a low molecular weight material andenhances the durability of the element. Furthermore, a high molecularweight material can be formed into a film by application and thereforemanufacture of the element is relatively easy.

The structure of a light emitting element using a high molecular weightorganic light emitting material is basically the same as the structureof a light emitting element using a low molecular weight organic lightemitting material, and has a cathode, an organic light emitting layer,and an anode. When an organic light emitting layer is formed from a highmolecular weight organic light emitting material, a two-layer structureis popular among the known ones. This is because it is difficult to forma laminate structure using a high molecular weight material unlike thecase of using a low molecular weight organic light emitting material.Specifically, an element using a high molecular weight organic lightemitting material has a cathode (an Al alloy), a light emitting layer, ahole transporting layer, and an anode (ITO). Ca may be employed as thecathode material in a light emitting element using a high molecularweight organic light emitting material.

The color of light emitted from an element is determined by the materialof its light emitting layer. Therefore, a light emitting element thatemits light of desired color can be formed by choosing an appropriatematerial. The high molecular weight organic light emitting material thatcan be used to form a light emitting layer is a polyparaphenylenevinylene-based material, a polyparaphenylene-based material, apolythiophen-based material, or a polyfluorene-based material.

The polyparaphenylene vinylene-based material is a derivative ofpoly(paraphenylene vinylene) (denoted by PPV), for example,poly(2,5-dialkoxy-1,4-phenylene vinylene) (denoted by RO-PPV),poly(2-(2′-ethyl-hexoxy)-5-metoxy-1,4-phenylene vinylene) (denoted byMEH-PPV), and poly(2-(dialkoxyphenyl)-1,4-phenylene vinylene) (denotedby ROPh-PPV).

The polyparaphenylene-based material is a derivative ofpolyparaphenylene (denoted by PPP), for example,poly(2,5-dialkoxy-1,4-phenylene) (denoted by RO-PPP) andpoly(2,5-dihexoxy-1,4-phenylene).

The polythiophene-based material is a derivative of polythiophene(denoted by PT), for example, poly(3-alkylthiophene) (denoted by PAT),poly(3-hexylthiophene) (denoted by PHT), poly(3-cyclohexylthiophene)(denoted by PCHT), poly(3-cyclohexyl-4-methylthiophene) (denoted byPCHMT), poly(3,4-dicyclohexylthiophene) (denoted by PDCHT),poly[3-(4-octylphenyl)-thiophene] (denoted by POPT), andpoly[3-(4-octylphenyl)-2,2 bithiophene] (denoted by PTOPT).

The polyfluorene-based material is a derivative of polyfluorene (denotedby PF), for example, poly(9,9-dialkylfluorene) (denoted by PDAF) andpoly(9,9-dioctylfluorene) (denoted by PDOF).

If a layer that is formed of a high molecular weight organic lightemitting material capable of transporting holes is sandwiched between ananode and a high molecular weight organic light emitting material layerthat emits light, injection of holes from the anode is improved. Thishole transporting material is generally dissolved into water togetherwith an acceptor material, and the solution is applied by spin coatingor the like. Since the hole transporting material is insoluble in anorganic solvent, the film thereof can form a laminate with theabove-mentioned organic light emitting material layer that emits light.

The high molecular weight organic light emitting material capable oftransporting holes is obtained by mixing PEDOT with camphor sulfonicacid (denoted by CSA) that serves as the acceptor material. A mixture ofpolyaniline (denoted by PANI) and polystyrene sulfonic acid (denoted byPSS) that serves as the acceptor material may also be used.

The structure of this embodiment may be freely combined with any of thestructures of Embodiments 1 through 14.

According to the present invention, the entire substrate on which anOLED is formed is sealed in vacuum using a plastic film that has asealing film, to thereby increase the effect of preventing degradationof the OLED due to moisture and oxygen and enhance the stability of theOLED. The present invention therefore can provide a highly reliablelight-emitting device.

The present invention has a laminate structure including a plurality ofinorganic insulating films and, even if one of the inorganic insulatingfilms is cracked, the rest of the inorganic insulating films effectivelyprevent moisture and oxygen from entering the organic light emittinglayer. With a laminate structure of the plurality of inorganicinsulating films, the present invention can effectively prevent moistureand oxygen from entering the organic light emitting layer even when thequality of the inorganic insulating films is degraded by low temperatureduring formation of the inorganic insulating film.

The internal stress of the entire insulating films can be relaxed if anorganic insulating film that is smaller in internal stress than theinorganic insulating films is interposed between the inorganicinsulating films. Compared to a single layer of inorganic insulatingfilm having the same thickness as the total thickness of the inorganicinsulating films sandwiching the organic insulating film, cracking dueto the internal stress takes place less frequently in the inorganicinsulating films sandwiching the organic insulating film.

Accordingly the inorganic insulating films sandwiching the organicinsulating film is more effective in preventing moisture and oxygen fromentering the organic light emitting layer than a single layer ofinorganic insulating film even if the total thickness of the inorganicinsulating films sandwiching the organic insulating film is equal to thethickness of the single layer inorganic insulating film. Furthermore,the inorganic insulating films sandwiching the organic insulating filmis strong against cracking due to the internal stress.

1. A display device comprising: a first substrate; a wiring formed overthe first substrate; a second substrate over the wiring; at least onecontact hole in the second substrate; a conductive resin provided in thecontact hole; and an FPC provided over the second substrate with adrying material interposed therebetween, the FPC electrically connectedto the wiring through the conductive resin.
 2. A display deviceaccording to claim 1, wherein the first substrate comprises a firstplastic substrate.
 3. A display device according to claim 1, wherein thefirst substrate comprises one selected from the group consisting ofpolyether sulfone, polycarbonate, polyethylene terephthalate, andpolyethylene naphthalate.
 4. A display device according to claim 1,wherein the second substrate comprises a second plastic substrate.
 5. Adisplay device according to claim 1, wherein the second substratecomprises one selected from the group consisting of polyether sulfone,polycarbonate, polyethylene terephthalate, and polyethylene naphthalate.6. A display device according to claim 1, wherein the display device isan active matrix type light-emitting device.
 7. A display deviceaccording to claim 1, wherein the display device is a passive typelight-emitting device.
 8. A display device according to claim 1, whereinthe display device is incorporated in at least one selected from thegroup consisting of a video camera, a digital camera, a goggle-typedisplay, a personal computer, and a portable telephone.
 9. A displaydevice comprising: a first substrate; a wiring formed over the firstsubstrate; a second substrate over the wiring; at least one taperedcontact hole in the second substrate; an FPC provided over the secondsubstrate with a drying material interposed therebetween, the FPCelectrically connected to the wiring; a plurality of insulating filmscovering the first substrate, the second substrate and a part of theFPC; and a plastic film covering the plurality of insulating films,wherein an internal stress of at least one of the plurality ofinsulating films is smaller than those of the other insulating films.10. A display device according to claim 9, wherein the first substratecomprises a first plastic substrate.
 11. A display device according toclaim 9, wherein the first substrate comprises one selected from thegroup consisting of polyether sulfone, polycarbonate, polyethyleneterephthalate, and polyethylene naphthalate.
 12. A display deviceaccording to claim 9, wherein the other insulating films comprise oneselected from the group consisting of silicon nitride, siliconoxynitride, aluminum oxide, aluminum nitride, aluminum oxynitride, andaluminum silicon oxynitride.
 13. A display device according to claim 9,wherein the at least one of the plurality of insulating films comprisesone selected from the group consisting of polyimide, acrylic, polyamide,polyimideamide, benzocyclobutene, an epoxy resin, polyethylene,polytetrafluoroethyelen, polystyrene, poly(p-phenylene vinylene),polyvinyl chloride, and a polyparaxylylene-based resin.
 14. A displaydevice according to claim 9, wherein the second substrate comprises asecond plastic substrate.
 15. A display device according to claim 9,wherein the second substrate comprises one selected from the groupconsisting of polyether sulfone, polycarbonate, polyethyleneterephthalate, and polyethylene naphthalate.
 16. A display deviceaccording to claim 9, wherein the plastic film is flexible.
 17. Adisplay device according to claim 9, wherein the plastic film comprisesat least one selected from the group consisting of polyester,polypropylene, polyvinyl chloride, polyvinyl fluoride, polystyrene,polyacrylonitrile, polyethylene terephthalate, and nylon.
 18. A displaydevice according to claim 9, wherein the display device is an activematrix type light-emitting device.
 19. A display device according toclaim 9, wherein the display device is a passive type light-emittingdevice.
 20. A display device according to claim 9, wherein the displaydevice is incorporated in at least one selected from the groupconsisting of a video camera, a digital camera, a goggle-type display, apersonal computer, and a portable telephone.
 21. A display deviceaccording to claim 9, wherein the plurality of insulating filmscomprises a first insulating film, a second insulating film covering thefirst insulating film, and a third insulating film covering the secondinsulating film.
 22. A light-emitting device according to claim 21,wherein at least one of the first insulating film and the thirdinsulating film comprises one selected from the group consisting ofsilicon nitride, silicon oxynitride, aluminum oxide, aluminum nitride,aluminum oxynitride, and aluminum silicon oxynitride.
 23. Alight-emitting device according to claim 21, wherein the secondinsulating film comprises one selected from the group consisting ofpolyimide, acrylic, polyamide, polyimideamide, benzocyclobutene, anepoxy resin, polyethylene, polytetrafluoroethyelen, polystyrene,poly(p-phenylene vinylene), polyvinyl chloride, and apolyparaxylylene-based resin.
 24. A display device comprising: a firstsubstrate; a wiring formed over the first substrate; a second substrateover the wiring; at least one contact hole in the second substrate; aconductive resin provided in the contact hole; an FPC provided over thesecond substrate with a drying material interposed therebetween, the FPCelectrically connected to the wiring through the conductive resin; aplurality of insulating films covering the first substrate, the secondsubstrate and a part of the FPC; and a plastic film covering theplurality of insulating films, wherein an internal stress of at leastone of the plurality of insulating films is smaller than those of theother insulating films.
 25. A display device according to claim 24,wherein the first substrate comprises a first plastic substrate.
 26. Adisplay device according to claim 24, wherein the first substratecomprises one selected from the group consisting of polyether sulfone,polycarbonate, polyethylene terephthalate, and polyethylene naphthalate.27. A display device according to claim 24, wherein the other insulatingfilms comprise one selected from the group consisting of siliconnitride, silicon oxynitride, aluminum oxide, aluminum nitride, aluminumoxynitride, and aluminum silicon oxynitride.
 28. A display deviceaccording to claim 24, wherein the at least one of the plurality ofinsulating films comprises one selected from the group consisting ofpolyimide, acrylic, polyamide, polyimideamide, benzocyclobutene, anepoxy resin, polyethylene, polytetrafluoroethyelen, polystyrene,poly(p-phenylene vinylene), polyvinyl chloride, and apolyparaxylylene-based resin.
 29. A display device according to claim24, wherein the second substrate comprises a second plastic substrate.30. A display device according to claim 24, wherein the second substratecomprises one selected from the group consisting of polyether sulfone,polycarbonate, polyethylene terephthalate, and polyethylene naphthalate.31. A display device according to claim 24, wherein the plastic film isflexible.
 32. A display device according to claim 24, wherein theplastic film comprises at least one selected from the group consistingof polyester, polypropylene, polyvinyl chloride, polyvinyl fluoride,polystyrene, polyacrylonitrile, polyethylene terephthalate, and nylon.33. A display device according to claim 24, wherein the display deviceis an active matrix type light-emitting device.
 34. A display deviceaccording to claim 24, wherein the display device is a passive typelight-emitting device.
 35. A display device according to claim 24,wherein the display device is incorporated in at least one selected fromthe group consisting of a video camera, a digital camera, a goggle-typedisplay, a personal computer, and a portable telephone.
 36. A displaydevice according to claim 24, wherein the plurality of insulating filmscomprises a first insulating film , a second insulating film coveringthe first insulating film, and a third insulating film covering thesecond insulating film.
 37. A light-emitting device according to claim36, wherein at least one of the first insulating film and the thirdinsulating film comprises one selected from the group consisting ofsilicon nitride, silicon oxynitride, aluminum oxide, aluminum nitride,aluminum oxynitride, and aluminum silicon oxynitride.
 38. Alight-emitting device according to claim 36, wherein the secondinsulating film comprises one selected from the group consisting ofpolyimide, acrylic, polyamide, polyimideamide, benzocyclobutene, anepoxy resin, polyethylene, polytetrafluoroethyelen, polystyrene,poly(p-phenylene vinylene), polyvinyl chloride, and apolyparaxylylene-based resin.
 39. A display device comprising: a firstsubstrate; a display element formed over the first substrate; a secondsubstrate over the display element; at least one contact hole in thesecond substrate; a conductive resin provided in the contact hole; andan FPC provided over the second substrate with a drying materialinterposed therebetween, the FPC electrically connected to the displayelement through the conductive resin.
 40. A display device according toclaim 39, wherein the first substrate comprises a first plasticsubstrate.
 41. A display device according to claim 39, wherein the firstsubstrate comprises one selected from the group consisting of polyethersulfone, polycarbonate, polyethylene terephthalate, and polyethylenenaphthalate.
 42. A display device according to claim 39, wherein thesecond substrate comprises a second plastic substrate.
 43. A displaydevice according to claim 39, wherein the second substrate comprises oneselected from the group consisting of polyether sulfone, polycarbonate,polyethylene terephthalate, and polyethylene naphthalate.
 44. A displaydevice according to claim 39, wherein the display element is alight-emitting element.
 45. A display device according to claim 39,wherein the display device is an active matrix type light-emittingdevice.
 46. A display device according to claim 39, wherein the displaydevice is a passive type light-emitting device.
 47. A display deviceaccording to claim 39, wherein the display device is incorporated in atleast one selected from the group consisting of a video camera, adigital camera, a goggle-type display, a personal computer, and aportable telephone.
 48. A display device comprising: a first substrate;a display element formed over the first substrate; a second substrateover the display element; at least one tapered contact hole in thesecond substrate; an FPC provided over the second substrate with adrying material interposed therebetween, the FPC electrically connectedto the display element; a plurality of insulating films covering thefirst substrate, the second substrate and a part of the FPC; and aplastic film covering the plurality of insulating films, wherein aninternal stress of at least one of the plurality of insulating films issmaller than those of the other insulating films.
 49. A display deviceaccording to claim 48, wherein the first substrate comprises a firstplastic substrate.
 50. A display device according to claim 48, whereinthe first substrate comprises one selected from the group consisting ofpolyether sulfone, polycarbonate, polyethylene terephthalate, andpolyethylene naphthalate.
 51. A display device according to claim 48,wherein the other insulating films comprise one selected from the groupconsisting of silicon nitride, silicon oxynitride, aluminum oxide,aluminum nitride, aluminum oxynitride, and aluminum silicon oxynitride.52. A display device according to claim 48, wherein the at least one ofthe plurality of insulating films comprises one selected from the groupconsisting of polyimide, acrylic, polyamide, polyimideamide,benzocyclobutene, an epoxy resin, polyethylene, polytetrafluoroethyelen,polystyrene, poly(p-phenylene vinylene), polyvinyl chloride, and apolyparaxylylene-based resin.
 53. A display device according to claim48, wherein the second substrate comprises a second plastic substrate.54. A display device according to claim 48, wherein the second substratecomprises one selected from the group consisting of polyether sulfone,polycarbonate, polyethylene terephthalate, and polyethylene naphthalate.55. A display device according to claim 48, wherein the plastic film isflexible.
 56. A display device according to claim 48, wherein theplastic film comprises at least one selected from the group consistingof polyester, polypropylene, polyvinyl chloride, polyvinyl fluoride,polystyrene, polyacrylonitrile, polyethylene terephthalate, and nylon.57. A display device according to claim 48, wherein the display elementis a light-emitting element.
 58. A display device according to claim 48,wherein the display device is an active matrix type light-emittingdevice.
 59. A display device according to claim 48, wherein the displaydevice is a passive type light-emitting device.
 60. A display deviceaccording to claim 48, wherein the display device is incorporated in atleast one selected from the group consisting of a video camera, adigital camera, a goggle-type display, a personal computer, and aportable telephone.
 61. A display device according to claim 48, whereinthe plurality of insulating films comprises a first insulating film, asecond insulating film covering the first insulating film, and a thirdinsulating film covering the second insulating film.
 62. Alight-emitting device according to claim 61, wherein at least one of thefirst insulating film and the third insulating film comprises oneselected from the group consisting of silicon nitride, siliconoxynitride, aluminum oxide, aluminum nitride, aluminum oxynitride, andaluminum silicon oxynitride.
 63. A light-emitting device according toclaim 61, wherein the second insulating film comprises one selected fromthe group consisting of polyimide, acrylic, polyamide, polyimideamide,benzocyclobutene, an epoxy resin, polyethylene, polytetrafluoroethyelen,polystyrene, poly(p-phenylene vinylene), polyvinyl chloride, and apolyparaxylylene-based resin.
 64. A display device comprising: a firstsubstrate; a display element formed over the first substrate; a secondsubstrate over the display element; at least one contact hole in thesecond substrate; a conductive resin provided in the contact hole; anFPC provided over the second substrate and with a drying materialinterposed therebetween, the FPC electrically connected to the displayelement through the conductive resin; a plurality of insulating filmscovering the first substrate, the second substrate and a part of theFPC; and a plastic film covering the plurality of insulating films,wherein an internal stress of at least one of the plurality ofinsulating films is smaller than those of the other insulating films.65. A display device according to claim 64, wherein the first substratecomprises a first plastic substrate.
 66. A display device according toclaim 64, wherein the first substrate comprises one selected from thegroup consisting of polyether sulfone, polycarbonate, polyethyleneterephthalate, and polyethylene naphthalate.
 67. A display deviceaccording to claim 64, wherein the other insulating films comprise oneselected from the group consisting of silicon nitride, siliconoxynitride, aluminum oxide, aluminum nitride, aluminum oxynitride, andaluminum silicon oxynitride.
 68. A display device according to claim 64,wherein the at least one of the plurality of insulating films comprisesone selected from the group consisting of polyimide, acrylic, polyamide,polyimideamide, benzocyclobutene, an epoxy resin, polyethylene,polytetrafluoroethyelen, polystyrene, poly(p-phenylene vinylene),polyvinyl chloride, and a polyparaxylylene-based resin.
 69. A displaydevice according to claim 64, wherein the second substrate comprises asecond plastic substrate.
 70. A display device according to claim 64,wherein the second substrate comprises one selected from the groupconsisting of polyether sulfone, polycarbonate, polyethyleneterephthalate, and polyethylene naphthalate.
 71. A display deviceaccording to claim 64, wherein the plastic film, is flexible.
 72. Adisplay device according to claim 64, wherein the plastic film comprisesat least one selected from the group consisting of polyester,polypropylene, polyvinyl chloride, polyvinyl fluoride, polystyrene,polyacrylonitrile, polyethylene terephthalate, and nylon.
 73. A displaydevice according to claim 64, wherein the display element is alight-emitting element.
 74. A display device according to claim 64,wherein the display device is an active matrix type light-emittingdevice.
 75. A display device according to claim 64, wherein the displaydevice is a passive type light-emitting device.
 76. A display deviceaccording to claim 64, wherein the display device is incorporated in atleast one selected from the group consisting of a video camera, adigital camera, a goggle-type display, a personal computer, and aportable telephone.
 77. A display device according to claim 64, whereinthe plurality of insulating films comprises a first insulating film, asecond insulating film covering the first insulating film, and a thirdinsulating film covering the second insulating film.
 78. Alight-emitting device according to claim 77, wherein at least one of thefirst insulating film and the third insulating film comprises oneselected from the group consisting of silicon nitride, siliconoxynitride, aluminum oxide, aluminum nitride, aluminum oxynitride, andaluminum silicon oxynitride.
 79. A light-emitting device according toclaim 77, wherein the second insulating film comprises one selected fromthe group consisting of polyimide, acrylic, polyamide, polyimideamide,benzocyclobutene, an epoxy resin, polyethylene, polytetrafluoroethyelen,polystyrene, poly(p-phenylene vinylene), polyvinyl chloride, and apolyparaxylylene-based resin.